FIREWALLS & NETWORK SECURITY with Intrusion Detection and VPNs, 2 nd ed. Chapter 10 Authenticating Users

FIREWALLS & NETWORK SECURITY with Intrusion Detection and VPNs, 2 nd ed. Chapter 10 Authenticating Users

Learning Objectives Explain why authentication is a critical aspect of network security Explain why firewalls authenticate and how they identify users Describe user, client, and session authentication List the advantages and disadvantages of popular centralized authentication systems Discuss the potential weaknesses of password security systems Discuss the use of password security tools Describe common authentication protocols used by firewalls Slide 2

The Authentication Process in General The act of identifying users and providing network services to them based on their identity Two forms Local authentication Centralized authentication service (often uses two-factor authentication) Slide 3

How Firewalls Implement the Authentication Process 1. Client makes request to access a resource 2. Firewall intercepts the request and prompts the user for name and password 3. User submits information to firewall 4. User is authenticated 5. Request is checked against firewall s rule base 6. If request matches existing allow rule, user is granted access 7. User accesses desired resources Slide 4

How Firewalls Implement the Authentication Process (continued) Slide 5

Firewall Authentication Methods User authentication Client authentication Session authentication Slide 6

User Authentication Basic authentication; user supplies username and password to access networked resources Users who need to legitimately access your internal servers must be added to your access control lists (ACLs) Slide 7

User Authentication (continued) Slide 8

Client Authentication Same as user authentication but with additional time limit or usage limit restrictions When configuring, set up one of two types of authentication systems Standard sign-on system Specific sign-on system Slide 9

Client Authentication (continued) Slide 10

Session Authentication Required any time the client establishes a session with a server of other networked resource Slide 11

Comparison of Authentication Methods Slide 12

Centralized Authentication Centralized server maintains all authorizations for users regardless of where user is located and how user connects to network Most common methods Kerberos TACACS+ (Terminal Access Controller Access Control System) RADIUS (Remote Authentication Dial-In User Service) Slide 13

Process of Centralized Authentication Slide 14

Kerberos Provides authentication and encryption through standard clients and servers Uses a Key Distribution Center (KDC) to issue tickets to those who want access to resources Used internally on Windows 2000/XP Advantages Passwords are not stored on the system Widely used in UNIX environment; enables authentication across operating systems Slide 15

Kerberos Authentication Slide 16

TACACS+ Latest and strongest version of a set of authentication protocols for dial-up access (Cisco Systems) Provides AAA services Authentication Authorization Auditing Uses MD5 algorithm to encrypt data Slide 17

RADIUS Centralized dial-in authentication service that uses UDP Transmits authentication packets unencrypted across the network Provides lower level of security than TACACS+ but more widely supported Slide 18

TACACS+ and RADIUS Compared Strength of security Filtering characteristics Proxy characteristics NAT characteristics Slide 19

Strength of Security Slide 20

Filtering Characteristics Slide 21

Proxy Characteristics RADIUS Doesn t work with generic proxy systems, but a RADIUS server can function as a proxy server TACACS+ Works with generic proxy systems Slide 22

NAT Characteristics RADIUS Doesn t work with NAT TACACS+ Should work through NAT systems Slide 23

Password Security Issues Passwords that can be cracked (accessed by an unauthorized user) Password vulnerabilities Lax security habits Slide 24

Passwords That Can Be Cracked Ways to crack passwords Find a way to authenticate without knowing the password Uncover password from system that holds it Guess the password To avoid the issue Protect passwords effectively Observe security habits Slide 25

Password Vulnerabilities Built-in vulnerabilities Often easy to guess Often stored visibly Social engineering To avoid the issues Choose complicated passwords Memorize passwords Never give passwords out to anyone Slide 26

Lax Security Habits To maintain some level of integrity, draw up a formal Memorandum of Understanding (MOU) Slide 27

Password Security Tools One-time password software Shadow password system Slide 28

One-Time Password Software Password is generated using a secret key Password is used only once, when the user authenticates Different passwords are used for each authentication session Types Challenge-response passwords Password list passwords Slide 29

Shadow Password System A feature of Linux that stores passwords in another file that has restricted access Passwords are stored only after being encrypted by a randomly generated value and an encoding formula Slide 30

Other Authentication Systems Single-password systems One-time password systems Certificate-based authentication 802.1x Wi-Fi authentication Slide 31

Single-Password Systems Operating system password Internal firewall password Slide 32

One-Time Password Systems Single Key (S/Key) SecurID Axent Pathways Defender Slide 33

Single Key (S/Key) Uses multiple-word rather than single word passwords User specifies single-word password and the number of times it is to be encrypted Password is processed by a hash function n times; resulting encrypted passwords are stored on the server Never stores original password on the server Slide 34

SecurID Uses two-factor authentication Physical object Piece of knowledge Most frequently used one-time password solution with FireWall-1 Slide 35

SecurID Tokens Slide 36

Axent Pathways Defender Uses two-factor authentication and a challengeresponse system Slide 37

Certificate-Based Authentication FireWall-1 supports the use of digital certificates to authenticate users Organization sets up a public key infrastructure (PKI) that generates keys to users User receives a code (public key) that is generated using the server s private key and uses the public key to send encrypted information to the server Server receives the public key and can decrypt the information using its private key Slide 38

802.1x Wi-Fi Authentication Supports wireless Ethernet connections Not supported by FireWall-1 802.1x protocol provides for authentication of users on wireless networks Wi-Fi uses Extensible Authentication Protocol (EAP) Slide 39

Wireless Authentication Slide 40

Chapter Summary Overview of authentication and its importance to network security How and why firewalls perform authentication services Types of authentication performed by firewalls User Client Session Slide 41

Chapter Summary (continued) Generally, users supply: Something they have (such as a smart card) or Something they know (such as a password) or Both Latest authentication systems measure or evaluate a physical attribute, such as a fingerprint or voiceprint Slide 42

Chapter Summary (continued) In a centralized authentication system: Firewall works with an authentication server Authentication server handles Username and password maintenance/generation Login requests Auditing Examples of centralized authentication systems: Kerberos TACACS+ RADIUS Slide 43

Chapter Summary (continued) Passwords Important part of virtually every authentication system Take one of two general forms: Single-word User password compared against database of passwords; access granted if match is made Vulnerable to ability of hackers to determine passwords, to user error, and to bad security habits One-time passwords Generated dynamically each time user attempts to log on to network Secret key used to generate single- or multipleword password Slide 44