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Table of Contents

Chapter 1
Network Security Principles ..................3

CCNA Security 640-554
Quick Reference

Chapter 2
Perimeter Security ............................... 23
Chapter 3
Cisco IOS Firewalls............................... 39
Chapter 4
Site-to-Site VPNs.................................. 50
Chapter 5
Cisco IOS IPS ........................................ 66
Chapter 6
LAN, SAN, Voice,
and Endpoint Security .......................... 79

Anthony Sequeira
CCIE, CCSI, VCP, Data Center Specialist

ciscopress.com

[2]
CCNA Security 640-554 Quick Reference

About the Author
Anthony Sequeira, CCIE No. 15626, is a Cisco Certified Systems Instructor and author regarding all levels and
tracks of Cisco Certification. Anthony formally began his career in the information technology industry in 1994 with
IBM in Tampa, Florida. He quickly formed his own computer consultancy, Computer Solutions, and then discovered
his true passion—teaching and writing about Microsoft and Cisco technologies. Anthony joined Mastering
Computers in 1996 and lectured to massive audiences around the world about the latest in computer technologies.
Mastering Computers became the revolutionary online training company KnowledgeNet, and Anthony trained there
for many years. Anthony is currently pursuing his second CCIE in the area of Security and is a full-time instructor
for the next generation of KnowledgeNet, StormWind Live.

About the Technical Editor
Sean Wilkinsis an accomplished networking consultant for SR-W Consulting (http://www.sr-wconsulting.com)
and has been in the field of IT since the mid 1990s working with companies such as Cisco, Lucent, Verizon and
AT&T. Sean currently holds certifications with Cisco (CCNP/CCDP), Microsoft (MCSE), and CompTIA (A+
and Network+). He also has a master’s of science degree in Information Technology with a focus in Network
Architecture and Design, a master’s of science degree in Organizational Management, a master’s certificate in
Network Security, a bachelor’s of science degree in Computer Networking, and an associate’s degree in Applied
Science in Computer Information Systems. In addition to working as a consultant, Sean spends a lot of his time as a
technical writer and editor for various companies.

© 2012 Pearson, Inc. All rights reserved. This publication is protected by copyright. Please see page 89 for more details.

External threats typically rely on technical methods to attack the network. Internal threats are the most serious. routers with access control lists (ACL). Firewalls. or in-house developers use insecure programming practices. This section also examines the different types of attacks that modern networks can experience. Why Do We Need Network Security? Network threats include internal and external threats.[3] CCNA Security 640-554 Quick Reference Chapter 1 Network Security Principles Network Security Fundamentals This section covers the need for network security and the security objectives found within most organizations. intrusion prevention systems (IPS). Please see page 89 for more details. Inc. blank or default passwords are used. The CCNA in Security focuses on combating these attacks using technical means. and other methods are the focus. Network Security Objectives Network security should provide the following: ■ Data confidentiality ■ Data integrity ■ Data and system availability © 2012 Pearson Education. These threats often occur because best practices are not followed. All rights reserved. For example. . This publication is protected by copyright.

This publication is protected by copyright. Data Classification Public-sector classification levels include the following: ■ Unclassified ■ Sensitive but unclassified (SBU) © 2012 Pearson Education. All rights reserved. Not all assets have the same value. A threat is a potential danger to information or systems. Please see page 89 for more details. Countermeasures are typically administrative.[4] Chapter 1: Network Security Principles Confidentiality ensures that only authorized individuals can view sensitive data. Information security risk is the measure of the impact of threat vectors exploiting the vulnerabilities of the assets you must to protect. and physical controls. An organization must classify its assets. Denial-of-service (DoS) attacks attempt to compromise data availability. protocol weaknesses. Assets. Common categories include policy flaws. or fail an entire network with a large quantity of information. Inc. Integrity ensures that data has not been changed by an unauthorized individual. A vulnerability is a weakness in a system or a design that might be exploited. Powerful methods to ensure confidentiality are encryption and access controls. and Threats Assets are anything of value to the organization. These attacks typically try to fail a system using an unexpected condition or input. Vulnerabilities. and software vulnerabilities. A countermeasure is a safeguard that mitigates against potential risks. technical. . Availability ensures that access to the data is uninterrupted. There is a National Vulnerability Database and also a Common Vulnerabilities and Exposures document.

■ Useful life: Information can be made obsolete with newer information.[5] Chapter 1: Network Security Principles ■ Confidential ■ Secret ■ Top-secret Private-sector classification levels include the following: ■ Public ■ Sensitive ■ Private ■ Confidential Classification criteria include the following: ■ Value: This is the most important factor. Please see page 89 for more details. All rights reserved. ■ Age: With time. . the sensitivity of data typically decreases. This publication is protected by copyright. Inc. Classification roles include the following: ■ Owner ■ Custodian (responsible for the day-to-day management of the data) ■ User © 2012 Pearson Education. ■ Personal association: The data is associated with sensitive issues or individuals.

Studying these attacks is the first step to defend against them. The system should not be shut down or rebooted before the investigation begins. Physical controls are mostly mechanical. deterrent. Inc. Network Attack Methodologies You must understand the command types of attacks that a network can experience. hardware. or detective. All rights reserved. opportunity. Please see page 89 for more details. and administrative law. © 2012 Pearson Education. . and software. and means. This publication is protected by copyright. Ethics refer to values that are even higher than the law. Controls are categorized as preventative. Technical controls involve electronics. Laws and Ethics Security policy must attempt to follow criminal. Responses Investigators must prove motive. civil.[6] Chapter 1: Network Security Principles Security Controls Administrative controls involve policies and procedures.

An exploit happens when computer code is developed to take advantage of a vulnerability. Please see page 89 for more details. All rights reserved. This publication is protected by copyright.[7] Chapter 1: Network Security Principles Motivations and Classes of Attack A vulnerability is a weakness in a system that can be exploited by a threat. The main vulnerabilities of systems are categorized as follows: ■ Design errors ■ Protocol weaknesses ■ Software vulnerabilities ■ Misconfiguration ■ Hostile code ■ Human factor Potential adversaries can include the following: ■ Nations or states ■ Terrorists ■ Criminals ■ Hackers ■ Corporate competitors ■ Disgruntled employees ■ Government agencies © 2012 Pearson Education. Inc. A risk is the likelihood that a specific attack will exploit a particular vulnerability of a system. .

■ Hacktivists: Individuals who have a political agenda in doing their work. 2. ■ Hobby hacker: Focuses mainly on computer and video games. ■ Academic hackers: People who enjoy designing software and building programs with a sense for aesthetics and playful cleverness. Manipulate users to gain access. Instead. Please see page 89 for more details. ■ Script kiddies: Individuals with low skill level. ■ Crackers (criminal hackers): Hackers with a criminal intent to harm information systems. Perform footprint analysis (reconnaissance). Install back doors. They do not write their own code. Inc. more skilled attackers. Gather additional passwords and secrets. © 2012 Pearson Education.[8] Chapter 1: Network Security Principles Many different classifications are assigned to hackers. 7. How Does a Hacker Usually Think? 1. and the modification of computer hardware and other electronic devices. 4. 6. 5. Leverage the compromised system. Enumerate applications and operating systems. This publication is protected by copyright. they run scripts written by other. including the following: ■ Hackers: Individuals who break into computer networks and systems to learn more about them. All rights reserved. . 3. ■ Phreakers (phone breakers): Individuals who compromise telephone systems. Escalate privileges. software cracking.

Inc. ■ Defend the computing environment. the attacker sends messages to a computer with an IP address that indicates the message is coming from a trusted host. Hackers can guess or predict the TCP sequence numbers that are used to construct a TCP packet without receiving any responses from the server. ■ Deploy IDS or IPS. ■ Use robust components. or a DoS type of attack. ■ Use robust key management. ■ Defend the enclave boundaries. In IP spoofing. Enumeration and Fingerprinting Ping sweeps and port scans are common practices to identify all devices and services on the network. IP spoofing is often the first step in the abuse of a network service. This publication is protected by copyright. ■ Build layered defenses. © 2012 Pearson Education. The basis of IP spoofing lies in an inherent security weakness in TCP known as sequence prediction. IP Spoofing IP spoofing refers to forging the source address information of a packet so that the packet appears to come from some other host in the network. Their prediction allows them to spoof a trusted host on a local network. Please see page 89 for more details. All rights reserved.[9] Chapter 1: Network Security Principles Defense in Depth The defense-in-depth strategy recommends several principles: ■ Defend in multiple places. These reconnaissance attacks are typically the first steps in a much larger more damaging attack. .

Source routing is the capability of the source to specify within the IP header a full routing path between endpoints. The attacker takes over communications with the server by spoofing the expected sequence number from the ACK previously sent from the legitimate client to the server. The attacker replies to the client using a modified packet with the source address of the server and the destination address of the client. The ACK packet contains the sequence number of the next packet that the client expects. Man-in-theMiddle Host A Host B R1 R2 Figure 1-1 Man-in-the-Middle Attack © 2012 Pearson Education. Inc. Cisco IOS routers drop all source-routed packets if the no ip sourceroute global command is configured. An attacker sniffs to identify the client and server IP addresses and relative port numbers. Man-in-the-middle attacks are often the result of TCP/IP spoofing. The attacker waits to receive an ACK packet from the client communicating with the server. Figure 1-1 shows a man-in-the-middle attack.[ 10 ] Chapter 1: Network Security Principles IP spoofing attacks are categorized in one of two ways: ■ Nonblind spoofing: The attacker sniffs the sequence and acknowledgment numbers and does not need to “predict” them. All rights reserved. This publication is protected by copyright. such as Cisco PIX 500 Series Security Appliances and the Cisco ASA 5500 Series Adaptive Security Appliances. . Security devices. drop such packets by default. This packet results in a reset that disconnects the legitimate client. Spoof attacks are often combined with IP source-routing options set in packets. ■ Blind spoofing: The attacker sends several packets to the target machine to sample sequence numbers and then predicts them for the attack. Please see page 89 for more details. The attacker then modifies his packet headers to spoof TCP/IP packets from the client.

■ Dumpster diving: Searching through company dumpsters. Steganography is an example of an overt channel: hiding messages in digital pictures and digitized audio. pharming. This publication is protected by copyright. Please see page 89 for more details. . and credit card details. such as usernames. and identity theft: Phishing is an attempt to criminally acquire sensitive information. ■ Emanations capturing: Capturing electrical transmissions from the equipment of an organization to obtain information about the organization. All rights reserved. ■ Overt channels: The ability to hide information within a transmission channel based on tunneling one protocol inside another.[ 11 ] Chapter 1: Network Security Principles Confidentiality Attacks Attackers can use many methods to compromise confidentiality. ■ Data diddling: Changing data before or as it is input into a computer. ■ Phishing. ■ Wiretapping: Monitoring the telephone or Internet conversations of a third party. Inc. Integrity Attacks Hackers can use many types of attacks to compromise integrity: ■ Salami attacks: A series of minor data security attacks that together result in a larger attack. ■ Covert channels: The ability to hide information within a transmission channel based on encoding data using another set of events. ■ Social engineering: Using social skills to manipulate people inside the network to provide the information needed to access the network. by masquerading as a trustworthy entity. Pharming is an attack aimed at redirecting the traffic of one website to another website. looking for information that can provide a valuable source of information for hackers. ■ Port scanning: Searching a network host for open ports. passwords. © 2012 Pearson Education. Following are some of the common methods: ■ Packet sniffing: Eavesdropping and logging traffic that passes over a digital network or part of a network.

■ Computer environment: Temperature. This is a form of DoS. malware that combines the characteristics of viruses. spyware. password. and others. water. Inc. and gas. Perhaps the trust relationship is between a system in the DMZ and a system in the inside network. ■ DoS (denial-of-service): An attack seeks to make a system or service unavailable after the system is sent large amounts of traffic. ■ Password attacks: Any attack that attempts to identify a user account.[ 12 ] Chapter 1: Network Security Principles ■ Trust exploits: An individual taking advantage of a trust relationship within a network. ■ DDoS (Distributed DoS): Hackers use a terminal to scan for systems to hack. ■ Electrical power: Attacks involve power loss. All rights reserved. ■ ICMP floods: The system is sent many false ICMP packets. airflow. or spikes. humidity. For example. Availability Attacks Hackers can use many types of attacks to compromise availability: ■ Botnets: A collection of software robots that run autonomously and automatically. worms. ■ SYN floods: The system is sent many different false SYN requests for TCP communication channels. ■ Session hijacking: The exploitation of a valid computer session to gain unauthorized access to information or services in a computer system. Blended Threats A growing trend is for attacks to combine techniques. This publication is protected by copyright. Please see page 89 for more details. or both. Trojan horses. reduction. . © 2012 Pearson Education. The hacker then installs zombie software on them.

■ Shut down unnecessary services and ports. ■ Develop a written security policy for the company. ■ Educate employees about the risks of social engineering. ■ Perform backups and test the backed-up files on a regular basis.[ 13 ] Chapter 1: Network Security Principles Best Practices for Mitigation These include the following: ■ Keep patches up-to-date. Security Architecture Design Guidelines ■ Defense in depth ■ Compartmentalization ■ Least privilege ■ Weakest link ■ Separation and rotation of duties ■ Hierarchically trusted components and protection © 2012 Pearson Education. ■ Use strong passwords. This publication is protected by copyright. ■ Control physical access to systems. ■ Implement security hardware and software. . ■ Avoid unnecessary web page inputs. ■ Encrypt and password-protect sensitive data. and change them often. All rights reserved. Please see page 89 for more details. Inc.

security planning. ■ Acquisition and development: Includes a risk assessment. and GLB Operation Security Secure Network Life Cycle Management A general system development life cycle (SDLC) includes five phases: ■ Initiation: Consists of a security categorization and a preliminary risk assessment. system integration. developmental security test and evaluation. and continuous monitoring. Inc. . © 2012 Pearson Education. FISMA. security certification. Please see page 89 for more details. security control development. and security accreditation. and hardware and software disposal. ■ Operations and maintenance: Includes configuration management and control. All rights reserved. This publication is protected by copyright. security assurance requirements analysis. media sanitization. and other planning components.[ 14 ] Chapter 1: Network Security Principles ■ Mediated access ■ Accountability and traceability ■ Regulatory compliance ■ Strengthened enforcement ■ Global spread of data breach notification laws ■ More prescriptive regulations ■ Growing requirements regarding third parties (business partners) ■ Risk-based compliance on the rise ■ Compliance process streamlined and automated ■ Examples: HIPAA. ■ Implementation: Includes inspection and acceptance. ■ Disposition: Includes information preservation. cost considerations and reporting. security functional requirements analysis.

This publication is protected by copyright.11 or wireless LAN testing) ■ Penetration testing The following list is a collection of popular tools: ■ Nmap ■ GFI LANguard ■ Tripwire ■ Nessus ■ Metasploit ■ SuperScan by Foundstone. All rights reserved. . a division of McAfee © 2012 Pearson Education. Inc.[ 15 ] Chapter 1: Network Security Principles Security Testing Many types of testing techniques are available: ■ Network scanning ■ Vulnerability scanning ■ Password cracking ■ Log review ■ Integrity checkers ■ Virus detection ■ War dialing ■ War driving (802. Please see page 89 for more details.

All rights reserved. eradication. recovery ■ Post-incident activities Computer Crime Investigations ■ Motive: Why did they do it? ■ Opportunity: Were they able to do it? ■ Means: Were they capable of doing it? Disaster Recovery Possible disruptions can be categorized as follows: ■ Nondisaster: A situation in which business operations are interrupted for a relatively short period of time.[ 16 ] Chapter 1: Network Security Principles Incident Management ■ Preparation ■ Detection and analysis ■ Containment. This publication is protected by copyright. ■ Business Continuity Concepts ■ Maximum Tolerable Downtime (MTD): The maximum length of time a business function can be discontinued without causing irreparable harm to the business © 2012 Pearson Education. and all operations must be moved. . ■ Catastrophe: The facilities are destroyed. Inc. ■ Disasters: These cause interruptions of at least a day. Please see page 89 for more details.

and advanced security. Borderless Networking Mobility is dissolving the borders of networks. The borderless end zone consists of intelligent endpoint traffic routing. A secure virtualized data center is another key component. All rights reserved. Please see page 89 for more details. Inc.[ 17 ] Chapter 1: Network Security Principles ■ Recovery Time Objective (RTO): The duration of time that a service level within a business process must be restored after a disaster (or disruption) in order to avoid unacceptable consequences associated with a break in business continuity ■ Recovery Point Objective (RPO): The maximum tolerable period in which data might be lost from an IT service due to a major incident Backups ■ Hot site: A completely redundant site with similar equipment to the original site. Borderless security products include the following: ■ Secure-X and context-aware security ■ Threat control and containment ■ Cloud security and data loss prevention ■ Secure connectivity through VPNs ■ Security management © 2012 Pearson Education. servers and routers). . It features broad coverage. ■ Cold site: Does not typically contain redundant computing equipment (for example. persistent connectivity. This publication is protected by copyright. ■ Warm site: A facility with similar equipment to the original site but is unlikely to have current data because of a lack of frequent replication with the original site.

Please see page 89 for more details. . The components of SecureX include the following: ■ Context awareness ■ Cisco AnyConnect Client ■ TrustSec: End-to-end security using security group tags on traffic ■ Cisco Security Intelligence Operations: Cloud-based security service Threats in cloud services ■ Abuse of cloud computing ■ Insecure interfaces and APIs ■ Malicious insiders ■ Shared technology issues ■ Data loss or leakage ■ Account or service hijacking ■ Unknown risk profile Network Foundation Protection Understanding the device planes: ■ Control plane. This publication is protected by copyright. high-level policy creation and enforcements for mobile users. such as routing protocols ■ Data plane. All rights reserved. forwarding of data packets ■ Management plane. Inc. used by management sessions © 2012 Pearson Education.[ 18 ] Chapter 1: Network Security Principles ■ ■ Cisco SecureX: SecureX is an access control strategy that enables effective.

Layer 2 controls. Secure Shell (SSH). Syslog. and AutoSecure ■ Management Plane: Authentication. Simple Network Management Protocol (SNMP). Network Time Protocol (NTP). and IOS Intrusion Prevention System (IPS) Developing a Network Security Policy This section details the creation of a network security policy—an important document that details the security objectives and procedures for the organization. All rights reserved. . and command-line interface (CLI) views ■ Data Plane: Access control lists (ACLs). Inc. Authorization.[ 19 ] Chapter 1: Network Security Principles Cisco NFP Toolkit ■ Control Plane: Control Plane Policing (CoPP). Transport Layer Security (TLS). © 2012 Pearson Education. Zone-Based Firewall. Please see page 89 for more details. Why Do You Need One? Aside from protecting organization assets. such as the following: ■ Making employees aware of their security-practice obligations ■ Identifying specific security solutions required to meet the goals of the security policy ■ Acting as a baseline for ongoing security monitoring Components of the Security Policy What are the components found in the network security policy? This section covers these details. This publication is protected by copyright. Control Plane Protection (CPPr). a security policy serves other purposes. Routing protocol authentication. and Accounting (AAA).

actions. a governing policy addresses security concepts deemed important to an organization. All rights reserved. This publication is protected by copyright. Please see page 89 for more details. Following are typical elements of this section: ■ Identification of the issue addressed by the policy ■ Discussion of the organization’s view of the issue ■ Examination of the relevance of the policy to the work environment ■ Explanation of how employees must comply with the policy ■ Enumeration of appropriate activities. Elements of this section include the following: ■ E-mail ■ Wireless networks ■ Remote access End-User Policies End-user policies address security issues and procedures relevant to end users. rather than the governing policy. Inc. and processes ■ Explanation of the consequences of noncompliance Technical Policies Technical policies provide a more detailed treatment of an organization’s security policy. © 2012 Pearson Education.[ 20 ] Chapter 1: Network Security Principles Governing Policy At a high level. .

this formula calculates the annualized loss expectancy (ALE). analysis must be performed of the probability that a threat will occur and the severity of that threat. ■ Qualitative analysis: Uses a scenario model. © 2012 Pearson Education. Please see page 89 for more details. A sample quantitative analysis formula is ALE = AV * EF * ARO. AV is an asset value. The ALE produces a monetary value that you can use to help justify the expense of security solutions. When performing risk analysis. EF is the exposure factor. This publication is protected by copyright. Senior security or IT personnel are usually directly involved with the creation of the security policy. and Avoidance Network designers identify threats to the network using threat identification practices.[ 21 ] Chapter 1: Network Security Principles More Detailed Documents More detailed documents are often contained in a security policy: ■ Standards: Support consistency within a network ■ Guidelines: Tend to be suggestions ■ Procedures: Detailed documents providing step-by-step instructions for completing specific tasks Roles and Responsibilities The ultimate responsibility for an organization’s security policy rests on the shoulders of senior management. and ARO is the annualized rate of occurrence. Also. This is risk analysis. Inc. you can use one of two approaches: ■ Quantitative analysis: Mathematically models the probability and severity of a risk. Senior management typically oversees the development of a security policy. All rights reserved. . Management. Examples of senior security or IT personnel include the following: ■ Chief security officer (CSO) ■ Chief information officer (CIO) ■ Chief information security officer (CISO) Risk Analysis. where scenarios of risk occurrence are identified.

Please see page 89 for more details. ■ Cisco Security Manager: Powerful but easy-to-use solution that enables you to centrally provision all aspects of device configurations and security policies for the Cisco family of security products ■ MARS (Cisco Security Monitoring. . All rights reserved. Inc. Benefits ■ Reduced integration costs ■ Proactive. ■ Adaptive: The network can intelligently evolve and adapt the threats. Analysis. ■ Collaborative: Collaboration occurs among the service and devices throughout the network. planned upgrades ■ Improves efficiency of security management Key Tools Note MARS is currently End of Sale/End of Life. This publication is protected by copyright. and Response System): Provides security monitoring for network security devices and host applications made by Cisco and other providers © 2012 Pearson Education.[ 22 ] Chapter 1: Network Security Principles Creating the Cisco Self-Defending Network This type of network is built in three phases: ■ Integrated: Every element is a point of defense.

1800 Series. Router Security Principles Following are three areas of router security: ■ Physical security ■ Operating system ■ Router hardening Cisco Integrated Services Router Family Cisco Integrated Services Routers feature comprehensive security services. Inc. voice. and 3800 Series. This section details exactly how you must do this. 2800 Series. and wireless in the platform portfolio for fast. scalable delivery of mission-critical business applications. All rights reserved. . Models include the 800 Series. Please see page 89 for more details. embedding data.[ 23 ] CCNA Security 640-554 Quick Reference Chapter 2 Perimeter Security Securing Administrative Access to Routers It is critical to secure administrative access to the routers that help power your network infrastructure. This publication is protected by copyright. © 2012 Pearson Education. security.

© 2012 Pearson Education. use the command service password-encryption. Please see page 89 for more details. use the command exec-timeout minutes [seconds]. . To configure idle timeouts for router lines. These commands can be used: ■ Console password line console 0 login password cisco ■ Virtual terminal password line vty 0 4 login password cisco ■ Enable password enable password cisco ■ Secret password enable secret cisco All these passwords are in clear text in the configuration files with the exception of the enable secret command. such as HTTP or Telnet/SSH. Inc. You must password-protect your router. To create username and password entries in the local accounts database. use no service password-recovery. All rights reserved. To encrypt the passwords that are clear text.[ 24 ] Chapter 2: Perimeter Security Configuring Secure Administrative Access You need to secure administrative access for local access (console port) and remote access. use the syntax username name secret { [0] password | 5 encrypted-secret}. You can also configure minimum password lengths with the security passwords min-length length command. This publication is protected by copyright. To disable the ability to access ROMMON to disable password recovery on your router.

The syntax for this command is privilege mode {level level command | reset command}. © 2012 Pearson Education. Use the command commands parser-mode {include | include-exclusive | exclude} [all] [interface interfacename | command] to assign commands to the selected view. To assign privileges to levels 2 through 14. STEP 2. To see these protected files. different administrators have different “views” of the CLI. Securing the Cisco IOS image and Configuration Files You can now secure copies of the IOS and your configuration file in memory so that they cannot be maliciously or accidentally erased. and the command secure boot-config protects the running configuration. complete the following steps: STEP 1. These protected files do not appear in a dir listing of flash.” If a user has level 13 access. All rights reserved. The secure boot-image command protects the IOS image. This publication is protected by copyright. Role-Based CLI Access A new approach to having various levels of access for different administrators is called role-based CLI access. Please see page 89 for more details. levels 1 through 14 are levels you can customize. Level 0 is reserved for user-level access privileges. Inc. There are 16 privilege levels. STEP 3. use the show secure bootset command. Enable AAA. Use the secret command to assign a password to the view. Using this approach. 0 through 15. STEP 5. These views contain the specific commands available for different administrators. Use the enable view command to enable the feature. STEP 6. Use the configure terminal command to enter global configuration mode. Verify using the enable view command. use the privilege command from the global configuration mode. To configure role-based CLI. . Use the parser view view-name command to create a new view. Remember that privilege levels “cascade.[ 25 ] Chapter 2: Perimeter Security Setting Multiple Privilege Levels You can configure multiple privilege levels on the router for different levels of your administrators. STEP 7. STEP 4. that user also gains access to the commands in levels 1 through 12. and level 15 is reserved for privileged mode commands.

© 2012 Pearson Education. . ■ show login Verifies that the login block-for command is issued. This command is mandatory. all other commands here are optional. The syntax for this command is banner {exec | incoming | login | motd | slip-ppp} d message d. This publication is protected by copyright.[ 26 ] Chapter 2: Perimeter Security Enhanced Security for Virtual Logins The following commands have been added to enhance security for virtual logins: ■ login block-for seconds attempts tries within seconds This command configures your Cisco IOS device for login parameters that help provide denial-of-service (DoS) detection. ■ login quiet-mode access-class {acl-name | acl-number} This command specifies an ACL that is to be applied to the router when it switches to quiet mode. Banner Messages Banner messages are important. Inc. ■ login delay seconds Configures a delay between successive login attempts. ■ login on-failure log [every login] Generates logging messages for failed login attempts. Please see page 89 for more details. With these messages. All rights reserved. The devices that match a permit statement in the ACL are exempt from the quiet period. ■ login on-success log [every login] Generates logging messages for successful login attempts. you can ensure that unauthorized personnel are informed that they will be prosecuted for illegal access.

Inc.com. configure the following services for CCP to access the router properly: ■ Set up a username and password that has privilege level 15: username name privilege 15 secret password ■ Enable the HTTP server: ip ip ip ip ■ http http http http server authentication local secure-server (for enabling HTTPS access to CCP) timeout-policy idle 600 life 86400 request 1000 Define the protocol to use to connect to the Telnet and Secure Shell (SSH) vty lines: line con 0 login local line vty 0 4 privilege level login local transport input line vty 5 15 privilege level login local transport input 15 telnet ssh 15 telnet ssh On a new router. All rights reserved.[ 27 ] Chapter 2: Perimeter Security Cisco Configuration Professional (CCP) CCP is a powerful graphical user interface you can use to configure and monitor your Cisco router. Please see page 89 for more details. you can access CCP from your PC web browser by going to http://10. © 2012 Pearson Education. This publication is protected by copyright.10. Supporting CCP CCP is factory-installed on some router models. If the router is an existing router and is not configured with the CCP default configuration. .10.1. It is also available on a CD-ROM included with new routers and can be downloaded from Cisco.

This section details the use of these services with a local database on the router or switch. ■ Communities: Groups of devices that share common components ■ Templates: Allows the simple replication of settings ■ User profiles: GUI views that provide role-based access control for different administrators Using AAA with the Local Database Authentication. authorization. Navigating in CCP Home. and User Profiles. Inc. These appear on the top button bar. and Monitor are the main buttons you need to use. Building Blocks for Ease of Management There are some new additions to the Cisco Configuration Professional that directly address the ease of management for larger environments. open an HTTP or HTTPS connection to the IP address of the Ethernet interface on the router. many options appear down the button bar on the left side of the screen. Templates. When you click either Configure or Monitor. This publication is protected by copyright. To launch CCP from the router flash memory. Configure. © 2012 Pearson Education. These features include Communities. . and accounting (AAA) services are a powerful security addition to any organization. All rights reserved. Many of these options lead to a wizard that aids in the configuration.[ 28 ] Chapter 2: Perimeter Security Running CCP To launch Cisco CCP from a PC. Please see page 89 for more details. choose Start > Programs (All Programs) > Cisco Systems > Cisco CCP > Cisco CCP.

Please see page 89 for more details. . For example. Then choose Configure > Router > AAA > Authentication Policies > Login to configure the local setting. To display the attributes collected for a AAA session. You can use AAA (pronounced “triple A”) to control administrative access to the device and access to the network through the device. and packet mode 0 (when the user tries to connect through the router for access to the network beyond). Authorization dictates what these users can do after they are authenticated. use the show aaa user {all | unique id} command in privileged EXEC © 2012 Pearson Education. To configure in CCP. Use the clear aaa local user lockout command in privileged EXEC mode to unlock a locked-out user. Inc. use the show aaa local user lockout command in privileged EXEC mode. use the aaa local authentication attempts max-fail command in global configuration mode. You can make additional settings at the command line. and Accounting Authentication requires users and administrators to prove that they actually are who they say they are. The two modes are character mode (when the user tries to connect to the router for admin). Then choose Configure > Router > AAA > AAA Summary to ensure that AAA is enabled. Accounting tracks what users do.[ 29 ] Chapter 2: Perimeter Security Authentication. and then the router authenticates using the local database. the user connects to the router. To display a list of all locked-out users. the router prompts for a username and password. choose Configure > Router > Router Access > User Accounts/View to add user accounts. to specify the maximum number of unsuccessful authentication attempts before a user is locked out. All rights reserved. Authorization. This publication is protected by copyright. Cisco provides four methods to implement AAA: ■ Self-contained AAA using the local database ■ Cisco Secure Access Control Server (ACS) for Microsoft Windows Server ■ Cisco Secure ACS Express (entry-level version appropriate for 350 users) ■ Cisco Secure ACS Solution Engine (rack-mountable hardware version) Local Authentication Using the local authentication method.

Of the two. use the debug aaa authentication command in privileged EXEC command mode. the Cisco device uses TACACS+ or RADIUS. TACACS+ offers the following features: ■ Separates authentication and authorization ■ Supports a large number of features ■ Encrypts all communications ■ Uses TCP port 49 RADIUS offers the following features: ■ Scales well ■ Uses UDP ports 1645 or 1812 for authentication and UDP ports 1646 or 1813 for accounting © 2012 Pearson Education. CCP creates the necessary commands at the CLI from the GUI.[ 30 ] Chapter 2: Perimeter Security mode. To display information about AAA authentication. Inc. Also. but RADIUS is an open standard. . Please see page 89 for more details. To communicate with the external Cisco Secure ACS. ■ The aaa authentication login default local command defines the default method list for login authentication using the local database. This publication is protected by copyright. Using AAA with Cisco Secure ACS ACS is a more scalable solution than trying to create and maintain user accounts on separate Cisco devices. All rights reserved. TACACS+ is more secure. ■ The username command adds a username and password to the local security database. many of the most modern security features require the use of the open-standard RADIUS protocol. CCP uses the following commands on the router: ■ The aaa new-model command enables AAA. You can use the show aaa sessions command to show the unique ID of a session.

This publication is protected by copyright. and so forth. It integrates the functionality of ACS and NAC solutions. Add router as AAA client. use CCP and choose Configure > Router > AAA > AAA Servers and Groups > Servers and add the servers. location. Configure identity groups and identity store. Inc. Then choose Configure > Router > AAA > Authentication Policies > Login to create a policy. STEP 2. New in ACS 5. STEP 5. To configure this rule-based approach in ACS. © 2012 Pearson Education. Implementing Secure Management and Reporting Management traffic is often a necessity in the network infrastructure. You can apply a policy that you create using Configure > Router > Router Access > VTY. This section details how to ensure that this traffic does not represent a security breach. Create an authorization policy. complete the following steps: STEP 1. date.[ 31 ] Chapter 2: Perimeter Security To configure the router for AAA with ACS. STEP 3. access type. Create an identity policy. Configure access services to process request. time. All rights reserved. . This would include access. Please see page 89 for more details. Rule-based policies provide a more flexible approach that can match on a variety of access conditions found in current networks. Cisco ISE The Cisco Identity Services Engine (ISE) is a next-generation identity and access control solution.2: Rule-Based Policies You can use this system to grant permissions on conditions other than the identity alone. STEP 4.

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The Architecture for Secure Management and Reporting
The information flow between management hosts and the managed devices can take two paths:

Out-of-band (OOB): Information flows within a network on which no production traffic resides.

In-band: Information flows across the enterprise production network.

Overall guidelines for secure management and reporting include the following:

Keep clocks on hosts and network devices synchronized.

Record changes and archive configurations.

OOB Management Guidelines
Help ensure that management traffic is not intercepted on the production network.

In-Band Management Guidelines

Apply only to those devices that truly need to be managed in this manner.

Use IPsec, SSH, or SSL.

Decide whether monitoring needs to be constant or periodic.

Syslog
Syslog is the current standard for logging system events in a Cisco infrastructure. It is the most popular option for storing Cisco router
log messages. The Cisco Security Monitoring, Analysis, and Response System (MARS) is a Cisco security appliance that can receive
and analyze syslog messages from various networking devices and hosts.

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[ 33 ]
Chapter 2: Perimeter Security

Router log messages can also be sent to using the following:

Console

Terminal lines

Internal buffer

SNMP traps

Figure 2-1 shows the various Cisco log severity levels.
Cisco router log messages contain three main parts:

Time stamp

Log message name and severity level

Message text

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[ 34 ]
Chapter 2: Perimeter Security

Level

Name

Description

0

Emergencies

A panic condition normally
broadcast to all users

1

Alerts

A condition that should be
corrected immediately, such as
a corrupted system database

2

Critical

Critical conditions; for example,
hard device errors

3

Errors

Errors

4

Warnings

Warning messages

5

Notifications

Conditions that are not error
conditions, but should possibly
be handled specially

6

Information

Informational messsages

7

Debugging

Messages that contain
information normally of use only
when debugging a program

Figure 2-1 Cisco Log Severity Levels
Figure 2-2 shows this message format.

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[ 35 ]
Chapter 2: Perimeter Security
Name and Severity Level
Date/Time

*Apr 27 17:31:13.389: %SYS-5-CONFIG_I: Configured from console by console

The Message Text

Figure 2-2 Cisco Log Message Format
To enable syslog log on your router using CCP, choose Configure > Router > Logging. To view the syslog information, choose
Monitor > Logging.

Simple Network Management Protocol (SNMP)
Versions 1 and 2c of SNMP use clear-text passwords called community strings. This offers little to no security.
SNMP 3 uses a combination of authenticating and encrypting packets over the network to provide secure access to devices. SNMP 3
provides message integrity, authentication, and encryption.
SNMP 3 supports all three of the following security levels:

noAuth: Community string

auth: HMAC or MD5 (hashing for integrity)

Priv: DES, 3DES, or AES (encryption for confidentiality)

When actually implemented on a router, these levels can be combined. For example, authPriv enables the use of authentication and
encryption.
To use the CCP to configure SNMP, choose Configure > Router > SNMP > Edit.
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Chapter 2: Perimeter Security

SSH
The SSH daemon is a feature that enables an SSH client to make a secure, encrypted connection to a Cisco router. Use SSH rather
than Telnet to manage Cisco devices. Cisco IOS Release 12.1(1)T and later support SSH Version 1 (SSHv1), and Cisco IOS Release
12.3(4)T and later support both SSHv1 and SSH Version 2 (SSHv2). The Cisco router acts as the SSH server, and the client must be
acquired to connect to the server. A sample client is PuTTY.
To use SDM to configure SSH, choose Configure > Additional Tasks > Router Access > SSH.
After enabling SSH on the router, configure the vty lines to support SSH. To use Cisco SDM to configure SSH on the vty lines,
choose Configure > Additional Tasks > Router Access > VTY.
To use the command line for the configuration, follow these steps:
STEP 1. Configure the IP domain name of your network using the ip domain-name domain_name command in global
configuration mode.
STEP 2. If there are any existing key pairs, overwrite them using the command crypto key zeroize rsa.
STEP 3. Generate keys to be used with SSH by generating RSA keys using the crypto key generate rsa generalkeys modulus modulus-size command in global configuration mode.
STEP 4. Configure how long the router waits for the SSH client to respond using the ip ssh timeout seconds command in global configuration mode; this step is optional.
STEP 5. Configure the number of SSH retries using the ip ssh authentication-retries integer command in
global configuration mode; this step is optional.
STEP 6. Enable vty inbound SSH sessions; use the transport input ssh command.

Locking Down the Router
Cisco provides two powerful methods for locking down the router. This means disabling or protecting unused services, and making
other configuration changes necessary for a secure network infrastructure.

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This provides a secure end-to-end solution for internetworking. ■ One-Step Lockdown does not support the enabling of TCP intercepts. it does not support the enabling of Service Control Point or the disabling of other access services and file transfer services. ■ One-Step Lockdown does not support the setting of Selective Packet Discard (SPD) values. choose Configure > Security > Security Audit > One Step Lockdown. . ■ Although One-Step Lockdown does support the disabling of SNMP. ■ Although One-Step Lockdown does support the configuration of SSH access. Following are some distinctions between the two approaches: ■ One-Step Lockdown does not support the disabling of NTP. ■ One-Step Lockdown does not support the configuration of AAA. IPv6 IPsec is the IETF standard for IPv6 network security. Please see page 89 for more details. © 2012 Pearson Education. and IPsec support is mandatory.[ 37 ] Chapter 2: Perimeter Security AutoSecure The AutoSecure IOS feature is invoked by issuing the auto secure command from the CLI. This publication is protected by copyright. Inc. it does not support the configuration of SNMP 3. CCP One-Step Lockdown The CCP One-Step Lockdown method for securing a router uses a wizard in the CCP graphical interface. You can also use an informative Security Audit feature before performing the One-Step Lockdown. All rights reserved. ■ One-Step Lockdown does not configure antispoofing access control lists. To access this feature.

■ End nodes exposed to many more threats such as address configuration. © 2012 Pearson Education. Please see page 89 for more details. Inc. ■ Consider current and future security enhancements. ■ Secure each protocol in transition approaches. ■ Tunneling and dual stacking become vulnerabilities. dual stack is preferred. ■ Reliance on multicast and ICMP Version 6.[ 38 ] Chapter 2: Perimeter Security Many of the threats faced in an IPv6 environment are the same found in an IPv4 environment. All rights reserved. . IPv6 has some new vulnerabilities: ■ Training and planning. ■ Header extensions can be exploited. Recommended Practices for IPv6 Security ■ Ingress filtering is key. Unfortunately. This publication is protected by copyright. ■ Control the use of tunneling.

■ Enforce the access control policy of the organization. Please see page 89 for more details. This section details their evolution and the technologies that have resulted. examining packets one at a time and are implemented on a Cisco router using access control lists (ACL). . Inc. Firewall Fundamentals The firewall should ■ Be resistant to attacks. Static Packet-Filtering Firewalls These work at Layers 3 and 4. This publication is protected by copyright.[ 39 ] CCNA Security 640-554 Quick Reference Chapter 3 Cisco IOS Firewalls Firewall Technologies Firewalls are a key security technology in the modern network infrastructure. Advantages of these firewalls include the following: ■ Based on simple permit and deny sets ■ Low impact on network performance © 2012 Pearson Education. ■ Be the only transit point. All rights reserved.

Proxy services are specific to the protocol that they are designed to forward and can provide increased access control. provide careful detailed checks for valid data. and generate audit records about the traffic they transfer. This publication is protected by copyright. Sometimes. All rights reserved. ■ Packet filters cannot dynamically filter certain services. ■ Packet filters do not filter fragmented packets well. 5. not devices ■ Make it harder for hackers to spoof and implement denial-of-service (DoS) attacks ■ Can monitor and filter application data ■ Can provide detailed logging © 2012 Pearson Education. ■ Complex ACLs are difficult to implement and maintain correctly.[ 40 ] Chapter 3: Cisco IOS Firewalls ■ Easy to implement ■ Supported on most routers ■ Initial security at a low network layer ■ Perform most of what high-end firewalls do at a lower cost Disadvantages of these firewalls include the following: ■ Susceptible to IP spoofing. they do not maintain any state information for added protection. ■ Packet filters are stateless. Application layer firewalls offer advantages: ■ Authenticate individuals. application layer firewalls support only a limited number of applications. Inc. Application Layer Gateways Application layer firewalls (also called proxy firewalls or application gateways) operate at Layers 3. . and 7 of the OSI model. 4. Please see page 89 for more details.

It tracks all sessions and inspects all packets passing through the firewall. it has some limitations: ■ Cannot prevent application layer attacks. too. although. © 2012 Pearson Education. ■ Not all protocols are stateful. The state table is part of the internal structure of the firewall.[ 41 ] Chapter 3: Cisco IOS Firewalls The disadvantages are as follows: ■ Process packets in software ■ Support a small number of applications ■ Sometimes require special client software ■ Are memory. ■ Does not support user authentication. Unlike static packet filtering. This publication is protected by copyright. . ■ Some applications open multiple connections. Please see page 89 for more details. for some applications it can analyze traffic at Layers 4 and 5. All rights reserved.and disk-intensive Dynamic or Stateful Packet-Filtering Firewalls Stateful inspection is a firewall architecture classified at the network layer. Although this is the primary Cisco Firewall technology. Stateful packet filtering maintains a state table and allows modification to the security rules dynamically. Inc. stateful inspection tracks each connection traversing all interfaces of the firewall and confirms that they are valid.

e-mail. All rights reserved. Cisco Firewall Family Cisco IOS Firewall features follow: ■ Zone-based policy framework for intuitive policy management ■ Application firewalling for web. and other traffic ■ Instant messenger and peer-to-peer application filtering ■ VoIP protocol firewalling ■ Virtual routing and forwarding (VRF) firewalling ■ Wireless integration ■ Stateful failover ■ Local URL whitelist and blacklist support.[ 42 ] Chapter 3: Cisco IOS Firewalls Other Types Application inspection firewalls ensure the security of applications and services. Inc. through Websense or SmartFilter © 2012 Pearson Education. This publication is protected by copyright. Advantages include the following: ■ Are aware of the state of Layer 4 and Layer 5 connections ■ Check the conformity of application commands at Layer 5 ■ Can and affect Layer 7 ■ Can prevent more kinds of attacks than stateful firewalls can Transparent firewalls (Cisco PIX and Cisco Adaptive Security Appliance Software Version 7. . Please see page 89 for more details. remote server support.0) can deploy a security appliance in a secure bridging mode as a Layer 2 device to provide security services at Layer 2 through Layer 7.

Please see page 89 for more details.[ 43 ] Chapter 3: Cisco IOS Firewalls Cisco PIX 500 Series Security Appliance features follow: ■ Advanced application-aware firewall services ■ Market-leading VoIP and multimedia security ■ Robust site-to-site and remote-access IP security (IPsec) VPN connectivity ■ Award-winning resiliency ■ Intelligent networking services ■ Flexible management solutions Cisco ASA 5500 Series Adaptive Security Appliance features follow: ■ World-class firewall ■ Voice and video security ■ SSL and IPsec VPN ■ IPS ■ Content security ■ Modular devices ■ High scalability Best Practices Firewall best practices include the following: ■ Position firewalls at key security boundaries. . This publication is protected by copyright. Inc. © 2012 Pearson Education. ■ Firewalls are the primary security device. but it is unwise to rely exclusively on a firewall for security. All rights reserved.

■ Remember that firewalls primarily protect from technical attacks originating from the outside. Cisco routers support two types of IP ACLs: ■ Standard ACLs: Check the source addresses of packets that can be routed. ■ Ensure that physical access to the firewall is controlled. port numbers. Please see page 89 for more details. They can also check for specific protocols. Analysis. ■ Outbound ACLs: Incoming packets are routed to the outbound interface and then are processed through the outbound ACL. Static Packet Filters Using ACLs Fundamentals of ACLs ACLs operate in two ways: ■ Inbound ACLs: Incoming packets are processed before they are routed to an outbound interface. If there is no matching permit or deny statement and the entire access list has been processed. . ■ Practice change management. © 2012 Pearson Education. and other parameters. All rights reserved. This publication is protected by copyright. the packet is denied by an implicit deny all at the end of the access list. Cisco Security Monitoring.[ 44 ] Chapter 3: Cisco IOS Firewalls ■ Deny all traffic by default and permit only services that are needed. and Response System (MARS) is especially useful in monitoring firewall logs. ■ Regularly monitor firewall logs. Inc. ■ Extended ACLs: Check both the source and destination packet addresses.

You must put the standard ACL as close as possible to the destination of the traffic you want to deny. and per interface is allowed. the ACL filters traffic going through the router but does not filter traffic that the router generates. This publication is protected by copyright. Please see page 89 for more details. ■ Only one ACL per protocol. ■ You should create the ACL before applying it to an interface.[ 45 ] Chapter 3: Cisco IOS Firewalls You can use two general methods to create ACLs: ■ Numbered ACLs: Use a number for identification. ■ Named ACLs: Use an alphanumeric string for identification. Inc. ■ If you apply an ACL to an interface. by default the ACL denies all traffic that fails to match any of the ACL lines. © 2012 Pearson Education.3 or later features IP access list entry sequence numbering to assist in the management of ACLs. Follow these guidelines with ACLs: ■ Based on the test conditions. per direction. ■ You should typically place extended ACLs as close as possible to the source of the traffic that you want to deny. ■ Unless you end your ACL with an explicit permit any statement. numbered. extended. ■ Your ACL should be organized to allow processing from the top down. . All rights reserved. Organize your ACL so that the more specific references to a network or subnet appear before ones that are more general. or named ACL. Cisco IOS Release 12. choose a standard. ■ Every ACL should have at least one permit statement.

■ Wildcard mask bit 1: Ignore the corresponding bit value in the address.15. For example.255.0 0.255. Instead of 255. The first two octets of the wildcard mask will be 0.40. Please see page 89 for more details.16.0. Inc. you can use the keyword host. © 2012 Pearson Education. instead of 0.40. .31. the administrator first converts the starting range number to binary: 16 = 0 0 0 1 0 0 0 0 Notice the administrator does not care about the binary values in the last four bit positions. you can use the keyword any. the administrator does not care at all about any bit in the last octet.255 Figure 3-1 Wildcard Masking You can use abbreviations in your wildcard masks.0.255.0.[ 46 ] Chapter 3: Cisco IOS Firewalls ACL Wildcard Masking Wildcard masking for IP address bits uses the numerals 1 and 0 to specify how to treat the corresponding IP address bits: ■ Wildcard mask bit 0: Match the corresponding bit value in the address.0/24. therefore. This publication is protected by copyright. Figure 3-1 shows an example of wildcard masking.40 must be matched exactly.0 since 172.16.0/24 to 172. so this octet is all 1 values: 1 1 1 1 1 1 1 1 = 255 The resulting address and wildcard mask used in the ACL are: 172. the wildcard mask is: 0 0 0 0 1 1 1 1 = 15 Also.40.0. For the third octet. All rights reserved. An administrator wants to match the subnets 172.

use ip access-group {access-list-number | access-list-name} {in | out} To assign an ACL to a vty line. This publication is protected by copyright. use access-class access-list-number {in [vrf-also] | out} To create an extended ACL. Inc. . use access-list access-list-number [dynamic dynamic-name [timeout minutes]] {deny | permit} protocol source source-wildcard destination destination-wildcard [precedence precedence] [tos tos] [log | log-input] [time-range time-range-name] [fragments] [established] Use the show access-list command to verify the ACL. The Cisco Configuration Professional (CCP) offers an excellent GUI for ACL creation. Please see page 89 for more details. All rights reserved. and use show ip interface to check for assignment.[ 47 ] Chapter 3: Cisco IOS Firewalls ACL Creation To create the standard ACL. The syntax is ipv6 traffic-filter to assign to the interface and ipv6 access-list to create. IPv6 Access Lists IPv6 access lists have the same structure and operational framework as in IPv4. Implicit entries exist at the end of each IPv6 ACL to enable neighbor discovery. © 2012 Pearson Education. use access-list access-list-number {deny | permit} source [source-wildcard] To assign the standard ACL to an interface. Choose Configure > Router > > ACL > ACL Editor. You can match on the extension headers.

■ Combining service lists with network and host address lists is allowed. ■ Application inspection. Please see page 89 for more details.and host-specific policies. ■ Policies are applied between zones. Overview Cisco IOS Release 12. All rights reserved.[ 48 ] Chapter 3: Cisco IOS Firewalls Cisco IOS Zone-Based Policy Firewall One of the most exciting developments for Cisco in the area of IOS Firewalls has been the new zone-based firewall. This new model presented the Cisco IOS zone-based policy. . Inc. ■ Default deny-all policy. © 2012 Pearson Education. ■ Virtual private network (VPN) VRF-aware Cisco IOS Firewall. ■ Subnet. including the following: ■ Stateful packet inspection. ■ URL filtering. This publication is protected by copyright. This section details this new technology. ■ DoS mitigation. which provides the following: ■ Intuitive policies for multiple interface routers ■ A greater level of granularity for firewall policy application ■ The ability to prohibit traffic between firewall zones until an explicit policy is applied to allow desirable traffic via a default deny-all policy The new zone-based policy inspection interface supports almost all the firewall features implemented in earlier releases and much more.4(6)T introduced a new configuration model for the Cisco IOS Firewall feature set.

Please see page 89 for more details.[ 49 ] Chapter 3: Cisco IOS Firewalls ■ Clearer statement of firewall policies. Inc. All rights reserved. . © 2012 Pearson Education. This publication is protected by copyright. From the Create Firewall tab. ■ Unidirectional policy between zones. navigate to Configure > Router > NAT > Create NAT > Configuration > Basic NAT. choose Configure > Security > Firewall > Firewall > Create Firewall > Basic Firewall. Start Basic NAT Wizard To configure Network Address Translation using the Basic NAT Wizard in the Cisco Configuration Professional (CPP). click Basic Firewall. Policies may be made up of combinations of the following: ■ IP addresses or subnets using ACLs ■ Protocols ■ Application services ■ Application-specific policies The zone-based firewall approach takes three possible actions: ■ Inspect: Causes Cisco IOS stateful packet inspection ■ Drop: Analogous to a deny statement in an ACL ■ Pass: Analogous to a permit statement in an ACL Configuring the Zone-Based Firewall with the Basic Firewall Wizard To configure a zone-based firewall using the Basic Firewall Wizard.

The Vigenère cipher is a polyalphabetic cipher that encrypts text by using a series of different Caesar ciphers based on the letters of a keyword. © 2012 Pearson Education. You should understand these principles before studying VPN technologies. Cryptanalysis is the practice of breaking codes to obtain the meaning of encrypted data.[ 50 ] CCNA Security 640-554 Quick Reference Chapter 4 Site-to-Site VPNs Cryptographic Services This section covers the key topics of cryptography. Inc. Overview Cryptology is the science of making and breaking secret codes. ■ A chosen-plain-text attack: The attacker chooses what data the encryption device encrypts and observes the cipher-text output. This publication is protected by copyright. ■ A cipher-text-only attack: The attacker has the cipher text of several messages but no knowledge of the underlying plain text. Following are examples of attacks: ■ Brute-force attack: The attacker tries every possible key with the decryption algorithm. A cipher is an algorithm for performing encryption and decryption. Please see page 89 for more details. . The attacker must deduce the key or keys used to encrypt the messages to decrypt other messages encrypted with the same keys. The attacker uses a brute-force attack to try keys until decryption with the correct key produces a meaningful result. All rights reserved. ■ A known-plain-text (the usual brute-force) attack: The attacker has access to the cipher text of several messages but also knows something about the plain text underlying that cipher text.

192-. All rights reserved. ■ Do not have export or import restrictions. ■ Create an avalanche effect. . Following are features that good encryption algorithms provide: ■ Resist cryptographic attacks. ■ Meet-in-the-middle attack: The attacker knows a portion of the plain text and the corresponding cipher text. and 256-bit keys ■ International Data Encryption Algorithm (IDEA): 128-bit keys © 2012 Pearson Education.and 168-bit keys ■ AES: 128-.[ 51 ] Chapter 4: Site-to-Site VPNs ■ A chosen-cipher-text attack: The attacker can choose different cipher texts to be decrypted and has access to the decrypted plain text. ■ Birthday attack: A form of brute-force attack against hash functions. which differ in their use of keys: ■ Symmetric encryption algorithms: Same key to encrypt and decrypt data ■ Asymmetric encryption algorithms: Different keys to encrypt and decrypt data The following are well-known encryption algorithms that use symmetric keys: ■ DES: 56-bit keys ■ Triple Data Encryption Standard (3DES): 112. Symmetric and Asymmetric Encryption Algorithms Following are two classes of encryption algorithms. Inc. Please see page 89 for more details. This publication is protected by copyright. ■ Support variable and long key lengths and scalability.

to 256-bit keys ■ RC5: 0. and 256-bit keys ■ Blowfish: 32. Unlike block ciphers. for many block ciphers is typically 128 bits. The best-known asymmetric cryptographic algorithms follow: ■ RSA ■ ElGamal ■ Elliptic curve algorithms Block ciphers transform a fixed-length block of plain text into a block of cipher text of the same length. Please see page 89 for more details.[ 52 ] Chapter 4: Site-to-Site VPNs ■ The RC series: RC2. typically bits.to 448-bit keys Because of their fast speed. Applying the reverse transformation to the cipher-text block. RC4. RC5. All rights reserved. the fixed length. © 2012 Pearson Education. stream ciphers operate on smaller units of plain text. depending on when they are encountered during the encryption process. with additional key management algorithms providing secure key exchange. 192-. With a stream cipher. Currently. also known as the block size. Inc. DES has a block size of 64 bits. RC4 is a common stream cipher. and RC6 ■ RC2: 40. the transformation of these smaller plain-text units varies.and 64-bit keys ■ RC4: 1. This publication is protected by copyright. . symmetric algorithms are frequently used for encryption services. results in decryption.to 2040-bit keys ■ RC6: 128-. using the same secret key.

STEP 4. Data of arbitrary length is input into the hash function. STEP 3. The steps of SSL VPN establishment follows: STEP 1. The user computer generates a shared-secret symmetric key that both parties use. The shared secret is encrypted with the public key of the router and transmitted to the router. © 2012 Pearson Education. Please see page 89 for more details. All rights reserved. Key Management Key management consists of the following components: ■ Key generation ■ Key verification ■ Key storage ■ Key exchange ■ Key revocation and destruction SSL VPNs SSL-based VPNs provide remote-access connectivity from almost any Internet-enabled location using a standard web browser and its native SSL encryption. The router software can easily decrypt the packet using its private key. typically using a web browser. STEP 5. which contains a public key digitally signed by a trusted certificate authority (CA). The router responds with a digital certificate. and the result of the hash function is the fixed-length hash. This publication is protected by copyright. The user makes an outbound connection to TCP port 443.[ 53 ] Chapter 4: Site-to-Site VPNs Cryptographic Hashes Hashing is a mechanism used for data integrity. . Inc. The key is used to encrypt the SSL session. STEP 2. Now both participants in the session know the shared secret key.

■ Use DES in CBC mode. ■ Cipher Block Chaining (CBC): Each 64-bit plain-text block is exclusive ORed (XORed) bitwise with the previous ciphertext block and then is encrypted using the DES key. where it encrypts data in 64-bit blocks. ■ Use 3DES rather than DES.[ 54 ] Chapter 4: Site-to-Site VPNs Symmetric Encryption Symmetric encryption is a common approach to encryption used with VPNs. Guidelines for DES usage include the following: ■ Change keys frequently to help prevent brute-force attacks. DES uses two standardized block cipher modes: ■ Electronic Code Book (ECB): Serially encrypts each 64-bit plain-text block using the same 56-bit key. DES This encryption algorithm typically operates in block mode. Lengths of 80 bits or longer are considered trusted. © 2012 Pearson Education. This section describes this important technology. Please see page 89 for more details. Inc. ■ Test a key to see whether it is weak before using it. . This publication is protected by copyright. Key Lengths Symmetric encryption algorithms typically use keys of length 40 to 256 bits. All rights reserved. ■ Use a secure channel to communicate the DES key from the sender to the receiver.

This provides nine different combinations of key length and block length. 192. low-latency environments. Rivest Ciphers Widely used RC algorithms include the following: ■ RC2: A variable key-size block cipher designed as a replacement for DES ■ RC4: A variable key-size Vernam stream cipher often used in file-encryption products and for secure communications © 2012 Pearson Education. and it cannot be hardware-based encryption. AES The AES algorithm currently specifies how to use keys with a length of 128. or 256 bits. and AES. . SEAL encryption uses a 160-bit encryption key and has less impact on the CPU compared to other software-based algorithms. This publication is protected by copyright. 3DES. or 256 bits to encrypt blocks with a length of 128. All rights reserved. AES is more suitable for high-throughput. Software-Optimized Encryption Algorithm (SEAL) SEAL is an alternative algorithm to software-based DES.[ 55 ] Chapter 4: Site-to-Site VPNs 3DES The technique of applying DES three times in a row to a plain-text block is called 3DES. especially if pure software encryption is used. AES was chosen to replace DES and 3DES because the key length of AES is much stronger than DES and AES runs faster than 3DES on comparable hardware. Inc. Restrictions for SEAL include the following: ■ The Cisco router and the other peer must support IPsec. This feature is available only on Cisco equipment. Both block length and key length can be extended easily in multiples of 32 bits. Please see page 89 for more details. 192. ■ The Cisco router and the other peer must support the k9 subsystem.

Sidney. data-integrity. and data-authenticity purposes: ■ IPsec gateways and clients use hashing algorithms to provide packet integrity and authenticity. based on the SHA-1 hashing algorithm Cisco products use hashing for entity-authentication. ■ Cisco IOS routers use hashing with secret keys to add authentication information to routing protocol updates. and Yin and is based on RC5 (meant to meet the design requirements of AES) Cryptographic Hashes This section details the most common cryptographic hashes in use today. such as that provided with file integrity checkers. Hash Message Authentication Codes (HMAC) Hashing is typically used for the following: ■ To provide proof of the integrity of data. Please see page 89 for more details. based on the MD5 hashing algorithm ■ Keyed SHA-1. All rights reserved. digitally signed contracts. and Public Key Infrastructure (PKI) certificates ■ To provide proof of authenticity when it is used with a symmetric secret authentication key. © 2012 Pearson Education. such as IPsec or routing protocol authentication Cisco technologies use two HMAC functions: ■ Keyed MD5. .[ 56 ] Chapter 4: Site-to-Site VPNs ■ RC5: A fast block cipher that has variable block size and variable key size ■ RC6: A block cipher designed by Rivest. This publication is protected by copyright. Inc.

Please see page 89 for more details.[ 57 ] Chapter 4: Site-to-Site VPNs ■ Cisco Software images have an MD5-based checksum available so that customers can check the integrity of downloaded images. ■ Hashing can also be used in a feedback-like mode to encrypt data. ■ Consider using MD5 only if speed is an issue. but the larger message digest makes it more secure against brute-force collision and inversion attacks. © 2012 Pearson Education. All rights reserved. 256-. The input is a data block plus a feedback of previous blocks. The algorithm is slightly slower than MD5. and 512-bit versions of SHA. The 512-bit blocks are divided into 16 32-bit sub-blocks. There are also 224-. . The output of the algorithm is a set of four 32-bit blocks. Best practices include the following: ■ Avoid MD5 if possible. ■ Protect HMAC secret keys. TACACS+ uses MD5 to encrypt its session. which concatenate to form a single 128-bit hash value. 384-. which consists of four rounds. MD5 MD5 is a one-way function that makes it easy to compute a hash from the given input data but makes it unfeasible to compute input data given only a hash. The message length is also encoded into the digest. SHA-1 The SHA-1 algorithm takes a message of no less than 264 bits in length and produces a 160-bit message digest. Inc. These blocks are then rearranged with simple operations in a main loop. This publication is protected by copyright.

only the signer knows this signature key. This publication is protected by copyright. Please see page 89 for more details. The user uses a signature algorithm with a personal signature key. Inc. which is usually public. STEP 5. The receiving device inputs the message. STEP 6. and the document was originated by the signer of the document. Cisco products use digital signatures for entity-authentication. ■ Cisco SSL endpoints and the Cisco Adaptive Security Device Manager (ASDM) use digital signatures to prove the identity of the SSL server. The sending device attaches the digital signature to the message and sends the message to the receiver. . data-integrity.[ 58 ] Chapter 4: Site-to-Site VPNs Digital Signatures Digital signatures are often used in the following situations: ■ To provide a unique proof of data source ■ To authenticate a user by using that person’s private key. All rights reserved. © 2012 Pearson Education. If the check is successful. called a digital signature. the signature algorithm generates its output. STEP 4. STEP 2. STEP 3. the digital signature. and the verification key into the verification algorithm. ■ Some of the service-provider-oriented voice management protocols use digital signatures to authenticate the involved parties. and the signature it generates ■ To prove the authenticity and integrity of PKI certificates ■ To provide a secure time stamp The following steps indicate how digital signatures function: STEP 1. Based on the input data and a signature key. and data-authenticity purposes: ■ IPsec gateways and clients use digital signatures to authenticate their Internet Key Exchange (IKE) sessions. The receiving device verifies the signature with the verification key. A user wants to sign some data. which checks the validity of the digital signature. the document was not changed after signing.

which is often a symmetric key. STEP 2. User A uses User B’s public key to encrypt a message. This publication is protected by copyright. User A transmits the encrypted message. nonrepudiation of data. The IKE protocol in IPsec VPNs uses DH algorithms extensively. a public key and a private key. STEP 4. User A acquires User B’s public key. and reveal. User B uses his private key to decrypt. The public key can be published. Inc. RSA is mainly used for two services: ■ To ensure confidentiality of data by performing encryption ■ To perform authentication of data. . the message. © 2012 Pearson Education. The RSA algorithm is based on the fact that each entity has two keys. but the private key must be kept secret. All rights reserved. STEP 3. using an agreed-upon algorithm. RSA The RSA keys are usually 512 to 2048 bits. Please see page 89 for more details.[ 59 ] Chapter 4: Site-to-Site VPNs Asymmetric Encryption Following are the steps used in asymmetric encryption: STEP 1. or both by generating digital signatures Diffie-Hellman (DH) The DH algorithm is the basis of most modern automatic key exchange methods.

509 is a well-known standard that defines basic PKI formats. ■ Certificate: A document that has been signed by the CA. or there may be a complex hierarchy of CAs. VPN Overview IPsec is the primary technology used in VPNs. authentication.[ 60 ] Chapter 4: Site-to-Site VPNs PKI A PKI provides a framework upon which you can base security services. Simple Certificate Enrollment Protocol (SCEP) is a PKI communication protocol used for automated VPN PKI enrollment. The CA may be a single entity. Two important PKI terms follow: ■ Certificate authority (CA): The trusted third party that signs the public keys of entities in a PKI-based system. Please see page 89 for more details. This publication is protected by copyright. All rights reserved. such as SSL and IPsec. It provides the following in the network: ■ Cost savings ■ Security ■ Scalability ■ Compatibility with broadband © 2012 Pearson Education. Inc. A PKI enables scalable solutions and is becoming an extremely important authentication solution for VPNs. The standard has been widely used with many Internet applications. and nonrepudiation. . such as encryption. Coverage includes critical topics such as the function of IPsec and IKE. This binds the name of the security entity with its public key. IPsec VPN Fundamentals This section ensures that you understand the fundamentals of the modern IPsec VPN. X.

[ 61 ] Chapter 4: Site-to-Site VPNs Following are two types: ■ Site-to-site ■ Remote-access Many Cisco devices can work together to form the VPN. This publication is protected by copyright. running over any number of networks. IPsec Overview IPsec has many advantages. upper layers are unaffected. All rights reserved. ■ Encapsulating Security Payload (ESP): Provides confidentiality and authentication. Inc. firewalls. it provides authentication of the IPsec traffic only. ■ IPsec is extremely scalable. as shown in Figure 4-1: ■ Authentication Header (AH): Used only when confidentiality is not required. using any number of media. IPsec features two main framework protocols. . ■ Security is provided at the network layer. © 2012 Pearson Education. Please see page 89 for more details. including routers. and Adaptive Security Appliances. including the following: ■ Offers protection for any number of applications.

Inc. The following are some of the standard algorithms that IPsec uses: ■ DES ■ 3DES ■ AES ■ MD5 © 2012 Pearson Education. Please see page 89 for more details. Transport mode protects the payload of the packet but leaves the original IP address in the clear. This publication is protected by copyright.[ 62 ] Chapter 4: Site-to-Site VPNs Authentication Header (AH) Data in plaintext R1 Provides: • Authentication • Integrity R2 Encapsulating Security Payload (ESP) Data encrypted R1 Provides: • Encryption • Authentication • Integrity R2 Figure 4-1 IPsec Security Protocols You can apply ESP and AH to IP packets in two different modes: ■ Transport mode: Security is provided only for the transport layer and above. All rights reserved. . ■ Tunnel mode: Encapsulates the original IP header and creates a new IP header that is sent unencrypted across the untrusted network. these hosts handle the encryption/decryption process. ESP transport mode is used between two hosts that are both configured to support IPsec.

. Phase 1 generates an Internet Security Association and Key Management Protocol (ISAKMP) SA.[ 63 ] Chapter 4: Site-to-Site VPNs ■ SHA-1 ■ DH IKE IPsec uses the IKE protocol for the following: ■ Negotiation of security association (SA) characteristics ■ Automatic key generation ■ Automatic key refresh ■ Manageable manual configuration IKE uses three modes of operation: ■ Main mode: An IKE session begins with one computer sending a proposal to another computer. All rights reserved. Inc. how long keys should remain active. Mode Config. which are for passing end-user data. ■ IKE Phase 2: SAs are negotiated by the IKE process ISAKMP on behalf of other services. The proposal sent by the initiator defines which encryption and authentication protocols are acceptable. IKE Phase 2 is used to build IPsec SAs. © 2012 Pearson Education. that need encryption key material for operation. IKE executes the following phases: ■ IKE Phase 1: Two IPsec peers perform the initial negotiation of SAs. ■ Quick mode: Similar to aggressive mode IKE negotiation. Additional service negotiations occur in IKE Phase 1. Please see page 89 for more details. and whether perfect forward secrecy should be enforced. except that negotiation is protected within an IKE SA. DPD. used for management traffic. ■ Aggressive mode: Compresses the IKE SA negotiation phases that are described thus far into three packets. and so on. This publication is protected by copyright. such as IPsec.

The definition of the transform set defines the parameters that the IPsec tunnel uses and can include the encryption and integrity algorithms. 2. Use the crypto isakmp policy command to define an IKE policy. 5. . © 2012 Pearson Education. Traffic is considered interesting when it travels between the IPsec peers and meets the criteria defined in the crypto ACL.[ 64 ] Chapter 4: Site-to-Site VPNs Site-to-Site VPN Construction This section details the exact steps in creating the popular site-to-site VPN. After the peers are authenticated. use show access-lists. Operations VPN negotiation occurs as follows: 1. Inc. 4. The IPsec tunnel terminates when the IPsec SAs are deleted or when their lifetime expires. Ensure that existing access lists are compatible with IPsec. VPN Configuration To configure a site-to-site IPsec VPN. follow these steps: 1. Please see page 89 for more details. In IKE Phase 1. Configure an ISAKMP policy to determine the ISAKMP parameters that will be used to establish the tunnel. 2. 3. All rights reserved. Define the IPsec transform set. the IPsec peers (Routers A and B) negotiate the established IKE SA policy. 4. The crypto ACL defines which traffic should be sent through the IPsec tunnel and be protected by the IPsec process. Use the crypto ipsec transform-set global configuration command. This publication is protected by copyright. The negotiation of the shared policy determines how the IPsec tunnel is established. Create a crypto ACL. An IPsec tunnel is initiated when Host A sends “interesting” traffic to Host B. 3. and data is transferred between the IPsec peers based on the IPsec parameters configured in the IPsec transform sets. In IKE Phase 2. The IPsec tunnel is created. a secure tunnel is created using ISAKMP. the IPsec peers use the authenticated and secure tunnel to negotiate IPsec SA transforms.

. Please see page 89 for more details.Verification commands include show crypto isakmp policy. there are restrictions on the interface that the VPN traffic uses (for example. Create and apply a crypto map. block all traffic that is not IPsec or IKE). This publication is protected by copyright.[ 65 ] Chapter 4: Site-to-Site VPNs 5. 6. Inc. and show crypto map. All rights reserved. VPN Configuration with CCP Choose Configure > Security > VPN to open the VPN page. Use the crypto map global configuration command and interface configuration command. The crypto map groups the previously configured parameters and defines the IPsec peer devices. The crypto map is applied to the outgoing interface of the VPN device. Configure the interface ACL. The CCP VPN Wizards use two sources to create a VPN connection: ■ User input during a step-by-step wizard process ■ Preconfigured VPN components The CCP provides some default VPN components: ■ Two IKE policies ■ An IPsec transform set for the Quick Setup Wizard © 2012 Pearson Education. show crypto ipsec transform-set. Usually.

You might add this powerful tool to your network via a dedicated hardware appliance known as a sensor. This publication is protected by copyright. or you might add this functionality using a network module inserted into a router or a switch. or it might be to prevent the attack from dropping the packet at a device. Inc. these copies of packets are received from another Cisco device (typically a switch). © 2012 Pearson Education.[ 66 ] CCNA Security 640-554 Quick Reference Chapter 5 Cisco IOS IPS Understanding Intrusion Prevention and Detection Cisco provides intrusion detection and prevention in a variety of ways in its current security portfolio. Prevention is possible by the sensor because it is operates inline with packet flows. Intrusion Prevention Versus Intrusion Detection Intrusion detection is powerful in that you can be notified when potential problems or attacks are introduced into your network. This action might be to alert the network administrator via an automated notification. Please see page 89 for more details. Sensors operating using intrusion detection run in promiscuous mode. . the goal is the same: to take some action based on an attack introduced to your network. Detection cannot prevent these attacks from occurring. However you decide to implement the technology. Intrusion prevention is more powerful in that potential threats and attacks can be stopped from entering your network. All rights reserved. or a particular network segment. Detection cannot prevent the attacks because it operates on copies of packets. Often.

There are two types of these alarms: false positive and false negative. False Alarms False alarms are IPS events that you do not want occurring in your implementation. Inc. Vulnerability A vulnerability is a weakness that compromises the security or functionality of a particular system in your network. Exploit An exploit is a mechanism designed to take advantage of vulnerabilities that exist in your systems. . For example. Both are unwanted. © 2012 Pearson Education. This is often viewed as the worst type of false alarm. Please see page 89 for more details. An example of a vulnerability is a web form on your public website that does not adequately filter inputs and guards against improper data entry. False Negative A false negative occurs when attack traffic does not trigger an alert on the IPS device. This publication is protected by copyright. This type of traffic is often referred to as benign traffic. An attacker might enter invalid characters in an attempt to corrupt the underlying database. a password-cracking package might be the exploit aimed at this vulnerability. if you have poor passwords in use in your network. but it was for traffic that does not constitute an actual attack. for obvious reasons. All rights reserved.[ 67 ] Chapter 5: Cisco IOS IPS IPS/IDS Terminology You should be aware of many security terms related to intrusion detection and prevention technologies. False Positive A false positive means that an alert has been triggered.

but it does not prevent the attack from entering the network or a network segment.[ 68 ] Chapter 5: Cisco IOS IPS True Alarms There are two types of true alarms in IPS terminology. Figure 5-1 shows an example of a promiscuous mode IDS implementation. True Positive A true positive means that an attack was recognized and responded to by the IPS device. Please see page 89 for more details. the device performs intrusion detection. Both true positives and true negatives are wanted. It can detect an attack and send an alert (and take other actions). Figure 5-2 shows an example of inline mode IPS. . This publication is protected by copyright. It cannot prevent the attack because it is not operating on traffic “inline” in the forwarding path. True Negative This means that nonoffending or benign traffic did not trigger an alarm. Inc. it can do prevention as opposed to mere detection. If a Cisco IPS device operates in inline mode. © 2012 Pearson Education. All rights reserved. This means that a device (often a switch) captures traffic for the sensor and forwards a copy for analysis to the sensor. This makes the device more effective against worms and atomic attacks (attacks that are carried out by a single packet). Promiscuous Versus Inline Mode IDS/IPS sensors operate in promiscuous mode by default. Because the device works with a copy of the traffic. This is because the IPS device is in the actual traffic path.

Inc. Please see page 89 for more details. This publication is protected by copyright.[ 69 ] Chapter 5: Cisco IOS IPS Copy of Attack Attack Management System Figure 5-1 Promiscuous Mode (IDS) © 2012 Pearson Education. All rights reserved. .

This is an example of an inline configuration in which only intrusion detection is performed. Cisco Intrusion Prevention System (IPS) Version 6. Please see page 89 for more details. whereas another segment features intrusion prevention protection. A sensor could be configured inline but could be set up so that it alerts only and doesn’t drop packets. Inc. This publication is protected by copyright. This pair of interfaces acts as a transparent Layer 2 structure that can drop an attack that fires a signature. © 2012 Pearson Education. All rights reserved.0 software permits a device to perform promiscuous mode and inline mode simultaneously.[ 70 ] Chapter 5: Cisco IOS IPS Attack Management System Figure 5-2 Inline Mode (IPS) To configure inline mode. you require two monitoring interfaces defined in the sensor as an inline pair. . This enables one segment to be monitored for intrusion detection only.

It attempts to discover activity that deviates from what an engineer defines as “normal” activity. The two common types of anomaly-based IPS are statistical anomaly detection and nonstatistical. This is much less prone to false positives and ensures that IPS devices are stopping common threats. As different types of attacks are created. Signature-Based Although Cisco uses a blend of detection and prevention technologies. signature-based IPS is the primary tool used by Cisco IPS solutions. The statistical approach learns about the traffic patterns on the network. All rights reserved. tuned. Alarms are triggered if activities are detected that violate the security policy coded by the organization. This publication is protected by copyright. Because it can be so difficult to define what is normal activity for a given network.[ 71 ] Chapter 5: Cisco IOS IPS Approaches to Intrusion Prevention A device can take many different approaches to securing the network using IPS. the security policy is “written” into the IPS device. Cisco releases signatures that are added to the device that identify a pattern that the most common attacks present. and updated to deal with the new attacks. this approach tends to be prone to a high number of false positives. Please see page 89 for more details. w this differs from signature-based. This type of approach is also known as pattern matching. © 2012 Pearson Education. Inc. Policy-Based With this type of technology. . these signatures can be added. Signature-based focuses on stopping common attacks. and the nonstatistical method uses information coded by the vendor. This section describes these various approaches. whereas policy-based is more concerned with enforcing the security policy of the organization. Anomaly-Based This type of IPS technology is often called profile-based.

hexadecimal representation. which now must engage in the resource-intensive process of reassembling the packets. Please see page 89 for more details. All rights reserved. Most signatures examine rather common settings. strings in the data are changed in minor ways in an attempt to evade detection. String Match In this type of attack. Obfuscation is one way in which control characters. Exploring Evasive Techniques Because attackers are aware of IPS technologies. not using fragmentation in the approach. the attacker breaks the attack packets into fragments so that they are more difficult to recognize.[ 72 ] Chapter 5: Cisco IOS IPS Protocol Analysis-Based Although this approach is similar to signature-based. the attacker spreads around the attack using a large number of small packets. . Fragmentation adds a layer of complexity for the sensor. Session In this type of attack. it looks deeper into packets thanks to a protocol-based inspection of the packet payload that can occur. You can use TCP segment reassembly to combat this evasive measure. Another string match type of evasive technique is to just change the case of the string. they have developed ways to counter these devices in an attempt to continue attacks on network systems. This publication is protected by copyright. © 2012 Pearson Education. Inc. but the protocol-analysis-based approach can do much deeper packet inspection and is more flexible in finding some types of attacks. Fragmentation With this evasive measure. or Unicode representation help to disguise the attack.

Often. Unlike the insertion attack. With this evasive procedure. the IPS sensor sees a different data stream than the end system because of the manipulation of the TTL field in the IP header. Inc. Because this method of foiling the IPS device exists. The attacker sends the attack via an encrypted session. All rights reserved. Evasion With this type of evasive technique.[ 73 ] Chapter 5: Cisco IOS IPS Insertion In this evasive technique. which results in an attack. . the attacker has the sensor see a different data stream than the intended victim. care must be taken to ensure that encrypted sessions cannot be established by attackers. Encryption-Based This is an effective means to have attacks enter the network. TTL-Based One way to implement an insertion attack is to manipulate the Time-To-Live (TTL) value of fragments. The encrypted attack cannot be detected by the IPS device. Resource Exhaustion Another evasive approach is to just overwhelm the sensor. © 2012 Pearson Education. the end system sees more data than the sensor. Please see page 89 for more details. This publication is protected by copyright. The end system ignores the harmless data and processes only the attack data. attackers simply try to overwhelm the physical device or the staff in charge of monitoring by flooding the device with alarm conditions. The IPS sensor does not fire an alert based on the harmless data. the attacker inserts data that is harmless along with the attack data.

and threat-rating system: The risk rating helps with alerts and is now based on many different components to improve the performance and operation of the sensor. Cisco Sensor Family The Cisco Sensor family includes the following devices: ■ Cisco IOS IPS ■ Cisco IDS Network Module ■ Cisco IDS 4215 Sensor ■ Cisco IDS 4240 Sensor © 2012 Pearson Education. This 6.0 version adds many new features. This CCNA Security Quick Reference focuses on Cisco products that can run Version 6. ■ Improved risk. This publication is protected by copyright. Please see page 89 for more details.[ 74 ] Chapter 5: Cisco IOS IPS Cisco Solutions and Products Cisco offers many products and solutions that address your need for intrusion detection/prevention in your network infrastructure. . ■ Anomaly detection: Designed to detect worm-infested hosts.0 of the Cisco IPS Sensor Software. ■ Passive operating system fingerprinting: A set of features that enables Cisco IPS to identify the OS of the victim of an attack. ■ External product interface: Enables sensors to subscribe for events from other devices. ■ New signature engines: Additions to cover Server Message Block and Transparent Network Substrate traffic. ■ Enhanced password recovery: Password recovery no longer requires reimaging. All rights reserved. Inc. including the following: ■ Virtualization support: Allowing different policies for different segments monitored by a single sensor. ■ Improved Cisco IPS Device Manager (IDM): New and improved GUI for management.

All rights reserved.0 software: ■ Cisco IDS 4235 Sensor ■ Cisco IDS 4250 XL Sensor Sensor Software Solutions Many options are available for configuration and management of Cisco sensors.[ 75 ] Chapter 5: Cisco IOS IPS ■ Cisco ASA AIP-SSM ■ Cisco IPS 4255 Sensor ■ Cisco Catalyst 6500 Series IDSM-2 ■ Cisco IPS 4260 Sensor The following legacy devices can also run IPS 6. the sensor operating systems and overall architecture is worth exploring for the certification exam and beyond. Telnet is disabled) ■ Intrusion Detection Application Programming Interface (IDAPI) ■ MainApp ■ SensorApp (for packet capture and analysis) ■ Sensor interfaces © 2012 Pearson Education. . Please see page 89 for more details. This publication is protected by copyright. Inc. The components include the following: ■ Event Store (provides storage for all events) ■ SSH and Telnet (by default. IPS Sensor Software Architecture IPS Sensor Software Version 6.0 runs on the Linux OS. Also.

All rights reserved.[ 76 ] Chapter 5: Cisco IOS IPS Management Options For single-device (element) management. Because the sensor is analyzing network traffic. options include the following: ■ Command-line interface (CLI) ■ Cisco IDM (a graphical user interface) For multiple-device management (enterprise management). options include the following: ■ Cisco IPS Event Viewer ■ Cisco Security Manager ■ Cisco Security MARS (Cisco Security Monitoring. © 2012 Pearson Education. The Cisco host IPS is called Cisco Security Agent. It complements network IPS by protecting the integrity of applications and operating systems. Inc. and Response System) Network IPS Network IPS refers to the deployment of devices (typically sensors) in the network that capture and analyze traffic as it traverses the network. Please see page 89 for more details. This publication is protected by copyright. This solution does not require additional hardware (sensors). . Analysis. Host IPS A host IPS solution features software installed on servers and workstations. it can protect many hosts at the same time.

■ Sensor placement: It is recommended that these be placed at those entry and exit points that provide sufficient IPS coverage. and the amount and type of traffic. Locations that generally need to be protected include the following: ■ Internet: Sensor between your perimeter gateway and the Internet ■ Extranet: Between your network and extranet connection ■ Internal: Between internal data centers ■ Remote access: Hardens perimeter control ■ Server farm: Network IPS at the perimeter and host IPS on the servers © 2012 Pearson Education. ■ Your management and monitoring options: The number of sensors often dictates the level of management you need. Please see page 89 for more details. Inc. connections. This publication is protected by copyright. .[ 77 ] Chapter 5: Cisco IOS IPS Deploying Sensors Technical factors to consider when selecting sensors for deployment in an organization include the following: ■ Network media in use ■ Performance of the sensor ■ Overall network design ■ IPS design (Will the sensor analyze and protect many systems or just a few?) ■ Virtualization (Will multiple virtual sensors be created in the sensor?) Important issues in an IPS design include the following: ■ Your network topology: Size and complexity. All rights reserved.

To view SDEE alarm messages in CCP. © 2012 Pearson Education. All rights reserved. choose Configure > Security > Advanced Security > Intrusion Prevention. . Inc. choose Monitor > Logging > SDEE Message Log. To view alarms generated by Cisco IOS IPS.[ 78 ] Chapter 5: Cisco IOS IPS Configuring Cisco IOS IPS Using Cisco Configuration Professional (CCP) Cisco IOS IPS signatures include the following advanced features: ■ Regular-expression string pattern matching ■ Support for various response actions ■ Alarm summarization ■ Threshold configuration ■ Anti-evasive techniques To configure IPS using the CCP. Please see page 89 for more details. choose Monitor > Logging > Syslog. This publication is protected by copyright.

■ Isolation between processes: An operating system should provide isolation between processes. and Endpoint Security Endpoint Security Securing endpoints in the network infrastructure is also important.[ 79 ] CCNA Security 640-554 Quick Reference Chapter 6 LAN. Cisco Security Agent. SAN. This publication is protected by copyright. This section details the Cisco approach to this important security area. Voice. Please see page 89 for more details. . Overview The Cisco strategy for addressing host security is based on three broad elements: ■ Endpoint protection: Cisco Security Agent protects endpoints against threats posed by viruses. Cisco NAC. Inc. and worms. Trojan horses. ■ Cisco Network Admission Control (NAC): Ensures that every endpoint complies with network security policies before being granted access to the network. The following techniques help protect an endpoint from operating system vulnerabilities: ■ Least-privilege concept: A process should never be given more privilege than is necessary to perform a job. this prevents rogue applications from affecting the operating system or other application. ■ Network infection containment: Containment focuses on automating key elements of the infection response process. © 2012 Pearson Education. and Intrusion Prevention System (IPS) provide this service. All rights reserved.

Inc. Rooting a system is hacking a system so that the attacker has root privileges. Please see page 89 for more details. ■ Penetrate phase: Exploit code is transferred to the vulnerable target. ■ Propagate phase: Extends the attack to other targets. easily verifiable pieces of software managed and monitored by a reference monitor. ■ Paralyze phase: Actual damage is done to the system. and Endpoint Security ■ Reference monitor: An access control concept that refers to a mechanism that mediates all access to operating system and application objects. All rights reserved. Buffer overflows are used to root a system or to cause a DoS attack. SAN. This publication is protected by copyright. Worm Attacks A worm attack consists of the following: ■ Enabling vulnerability ■ Propagation mechanism ■ Payload The worm attack occurs in phases: ■ Probe phase: Identifies vulnerable targets. verifiable pieces of code: Small. ■ Small. . Voice. Buffer Overflows Buffer overflow exploits overwrite memory on an application stack by supplying too much data into an input buffer. ■ Persist phase: The code tries to persist on the target system.[ 80 ] Chapter 6: LAN. © 2012 Pearson Education.

This publication is protected by copyright. and Endpoint Security IronPort Cisco IronPort security appliances protect enterprises against Internet threats. Please see page 89 for more details. Voice. . The following are the security appliance products that IronPort offers: ■ IronPort C-Series: E-mail security appliances ■ IronPort S-Series: Web security appliance ■ IronPort M-Series: Security management appliance Cisco NAC Cisco NAC products are designed to allow only authorized and compliant systems to access the network and to enforce network security policy.[ 81 ] Chapter 6: LAN. All rights reserved. Inc. The Cisco NAC Appliance includes the following components: ■ Cisco NAC Appliance Server (NAS): Performs network access control ■ Cisco NAC Appliance Manager (NAM): Centralized administrative interface ■ Cisco NAC Appliance Agent (NAA): Client software that facilitates network admission ■ Rule-set updates: Automatic updates Cisco Security Agent This product consists of the following: ■ Management Center for Cisco Security Agents ■ Cisco Security Agent © 2012 Pearson Education. with a focus on e-mail and web security products. SAN.

manage. Logical Unit Number Masking In computer storage. © 2012 Pearson Education. Gigabit Ethernet. This topic is explored in this section. and optical network. This publication is protected by copyright. and protect growing information resources across a consolidated Fibre Channel. Inc. All rights reserved. SAN. reliable access among servers and external storage resources. Voice. with a special emphasis on security for SANs. Cisco solutions for intelligent SANs provide a better way to access. LUN masking is an authorization process that makes a LUN available to some hosts and unavailable to others. Please see page 89 for more details. Internet Small Computer Systems Interface (iSCSI). a logical unit number (LUN) is an address for an individual disk drive and the disk device itself. and Endpoint Security Protection of end systems is provided by the following: ■ File system interceptor ■ Network interceptor ■ Configuration interceptor ■ Execution space interceptor Storage-Area Network Security Storage-area networking is another topic becoming more important. Fibre Channel over IP (FCIP). Overview A storage-area network (SAN) is a specialized network that enables fast.[ 82 ] Chapter 6: LAN. .

Please see page 89 for more details. . Zoning can use WWNs to assign security permissions. SAN Security Scope SAN security should focus on six areas: ■ SAN management access ■ Fabric access ■ Target access ■ SAN protocol ■ IP storage access ■ Data integrity and secrecy © 2012 Pearson Education. Inc. If a SAN contains several storage devices. This publication is protected by copyright. Voice. Fibre Channel Fabric Zoning Fibre Channel zoning is the partitioning of a Fibre Channel fabric into smaller subsets. Virtual SAN A virtual storage-area network (VSAN) is a collection of ports from a set of connected Fibre Channel switches that form a virtual fabric. one device should not necessarily be allowed to interact with all the other devices in the SAN. Zoning can also use name servers in the switches to either allow or block access to particular WWNs in the fabric. You can partition ports within a single switch into multiple VSANs. All rights reserved. SAN. and Endpoint Security World Wide Names A World Wide Name (WWN) is a 64-bit address that Fibre Channel networks use to uniquely identify each element in a Fibre Channel network.[ 83 ] Chapter 6: LAN.

. but it is more flexible in its support for gateways and applications. Media Gateway Control Protocol enables a client (for example. This section details this technology and lists important related security topics. ■ H. SAN. This publication is protected by copyright. such as VoIP gateways and gatekeepers. Overview You can find the following components in the VoIP network: ■ IP phones: ■ Call agents: Replace many of the features previously provided by PBXs ■ Gateways: Can forward calls between different types of networks ■ Gatekeepers: Can be thought of as the “traffic cops” of the WAN ■ Multipoint control units (MCU): Useful for conference calling ■ Application servers: Offer additional services such as voice mail ■ Videoconference stations: Devices/software that allow a calling or called party to view/transmit video as part of their telephone conversation Common VoIP protocols include the following: ■ H. All rights reserved. an analog port in a voice-enabled router) to communicate with a server (for example. It defines the necessary control mechanism to allow a media gateway controller to control gateways to support multimedia streams across networks.[ 84 ] Chapter 6: LAN. Please see page 89 for more details.248 is similar to MGCP. ■ SIP: Session Initiation Protocol is a popular protocol to use in mixed-vendor environments. Inc. a Cisco Unified Communications server) via a series of events and signals. ■ MGCP: Originally developed by Cisco. Voice.248: H.323: A suite of protocols that also defines certain devices. © 2012 Pearson Education. and Endpoint Security Voice Security Voice over IP is becoming more popular.

but refers to maliciously collecting such information over the phone) ■ SIP attacks (man-in-the-middle attacks and manipulation of SIP messages) Protection Mechanisms Mechanisms and methods to help secure the VoIP network include the following: ■ Auxiliary VLANs (with voice traffic getting its own VLAN). © 2012 Pearson Education. All rights reserved. ■ Security appliances. SAN. ■ SRTP: Secure RTP secures the RTP traffic. This publication is protected by copyright. or SPIT) ■ Vishing (similar to phishing. ■ Use IPsec protected VPNs. Common Voice Security Issues Common attacks include the following: ■ Accessing VoIP resources without proper credentials ■ Gleaning information from unsecured networks ■ Launching a denial-of-service (DoS) attack ■ Capturing telephone conversations ■ VoIP spam (more commonly referred to as spam over IP telephony. Inc. ■ RTP: Real-time Transport Protocol carries the voice payload. and Endpoint Security ■ SCCP: Skinny Client Control Protocol is a Cisco-proprietary signaling protocol. Voice. Please see page 89 for more details. . ■ RTCP: RTP Control Protocol provides information about an RTP flow.[ 85 ] Chapter 6: LAN.

Also. This section details many important security practices you must follow. Inc.1Q information in the frame and using the native VLAN. Please see page 89 for more details. . SAN. and Endpoint Security ■ Disable web access. ■ Root Guard: Denies a new root switch from being elected in the topology from an unauthorized port. All rights reserved. This publication is protected by copyright. © 2012 Pearson Education. VLAN Hopping Attackers can send traffic into another VLAN by double-tagging 802. but it should not be. ensure that switch ports are not using Dynamic Trunking Protocol (DTP) by using the switchport nonegotiate command. STP Protections Consider the following protection mechanisms: ■ BPDU Guard: Ensures that bridges plugged into PortFast ports do not cause a temporary Layer 2 loop. ■ Disable unneeded services. One easy way to combat this is to create an empty VLAN for the native VLAN and then use this as the native VLAN on all links.[ 86 ] Chapter 6: LAN. ■ Disable gratuitous ARP. Voice. Mitigating Layer 2 Attacks Layer 2 is often omitted from security practices.

or multicast frames in the LAN ■ MAC address notifications: Alerts when the MAC address on a port changes Layer 2 Best Practices Layer 2 best practices include the following: ■ Manage switches securely. ■ Use port security.[ 87 ] Chapter 6: LAN. use the command switchport port-security. Please see page 89 for more details. broadcast. ■ Selectively use Simple Network Management Protocol (SNMP). Inc. ■ Set user ports to nontrunking. To enable the feature and configure options. Switch1(config)# switchport port-security Switch1(config)# switchport port-security maximum 2 Switch1(config)# switchport port-security violation restrict Switch1(config)# switchport port-security aging time 120 Figure 6-1 Port Security Additional Security Features ■ Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN): Copy frames to a destination port for analysis ■ Storm control: Prevents an excess of unicast. © 2012 Pearson Education. ■ Do not use VLAN 1. . Figure 6-1 shows an example of port security configurations. and Endpoint Security Port Security Use this feature to lock down a port for authorized MAC address usage. SAN. ■ Use a dedicated VLAN for trunks. Voice. All rights reserved. This publication is protected by copyright.

Inc. and Endpoint Security ■ Enable STP security features. and place them in a VLAN. Voice. . ■ Trim Cisco Discovery Protocol (CDP).[ 88 ] Chapter 6: LAN. All rights reserved. ■ Disable unused ports. © 2012 Pearson Education. Please see page 89 for more details. This publication is protected by copyright. SAN.

[ 89 ] CCNA Security 640-554 Quick Reference CCNA Security 640-554 Quick Reference Anthony Sequeira Copyright © 2012 Pearson Education... our goal is to create in-depth technical books of the highest quality and value. undergoing rigorous development that involves the unique expertise of members of the professional technical community. including photocopying. If you have any comments on how we could improve the quality of this digital Quick Reference. please contact: U. marketing focus. shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this digital Quick Reference. and Cisco Systems. recording. without written permission from the publisher. and branding interests.com. Each book is crafted with care and precision. electronic or mechanical. All rights reserved. which may include electronic versions and/or custom covers and content particular to your business. © 2012 Pearson Education. Inc. Published by Cisco Press 800 East 96th Street Indianapolis. Inc.com. The author. . cannot attest to the accuracy of this information. Use of a term in this digital Quick Reference should not be regarded as affecting the validity of any trademark or service mark. Feedback Information At Cisco Press.com The opinions expressed in this digital Quick Reference belong to the author and are not necessarily those of Cisco Systems. First Release May 2012 ISBN-13: 978-1-58714-317-5 Warning and Disclaimer This digital Quick Reference is designed to provide information about the CCNA Security Certification. but no warranty or fitness is implied. Please be sure to include the digital Quick Reference title and ISBN in your message. Inc. This publication is protected by copyright. Indiana 46240 USA All rights reserved. We greatly appreciate your assistance. For more information. No part of this digital Quick Reference may be reproduced or transmitted in any form or by any means.S. For sales outside the United States please contact: International Sales international@pearsoned. except for the inclusion of brief quotations in a review. Every effort has been made to make this digital Quick Reference as complete and accurate as possible. Reader feedback is a natural continuation of this process. or otherwise alter it to better suit your needs. you can contact us through e-mail at feedback@ciscopress. Corporate and Government Sales The publisher offers excellent discounts on this digital Quick Reference when ordered in quantity for bulk purchases or special sales. Inc. The information is provided on an “as is” basis. Inc. Cisco Press or Cisco Systems. or by any information storage and retrieval system. training goals. Corporate and Government Sales 1-800-382-3419 corpsales@pearsontechgroup. Cisco Press. Trademark Acknowledgments All terms mentioned in this digital Quick Reference that are known to be trademarks or service marks have been appropriately capitalized.