ISA 3200 NETWORK SECURITY 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 2 7/14 IS 3200, Summer 2010

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) 3 7/14 IS 3200, Summer 2010

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 4 7/14 IS 3200, Summer 2010

How Firewalls Implement the Authentication Process (continued) 5 7/14 IS 3200, Summer 2010

Firewall Authentication Methods  User authentication  Client authentication  Session authentication 6 7/14 IS 3200, Summer 2010

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) 7 7/14 IS 3200, Summer 2010

User Authentication (continued) 8 7/14 IS 3200, Summer 2010

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 9 7/14 IS 3200, Summer 2010

Client Authentication (continued) 10 7/14 IS 3200, Summer 2010

Session Authentication  Required any time the client establishes a session with a server of other networked resource 11 7/14 IS 3200, Summer 2010

Comparison of Authentication Methods 12 7/14 IS 3200, Summer 2010

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) 13 7/14 IS 3200, Summer 2010

Process of Centralized Authentication 14 7/14 IS 3200, Summer 2010

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 15 7/14 IS 3200, Summer 2010

Kerberos Authentication 16 7/14 IS 3200, Summer 2010

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 17 7/14 IS 3200, Summer 2010

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 18 7/14 IS 3200, Summer 2010

TACACS+ and RADIUS Compared  Strength of security  Filtering characteristics  Proxy characteristics  NAT characteristics 19 7/14 IS 3200, Summer 2010

Strength of Security 20 7/14 IS 3200, Summer 2010

Filtering Characteristics 21 7/14 IS 3200, Summer 2010

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 22 7/14 IS 3200, Summer 2010

NAT Characteristics  RADIUS  Doesn’t work with NAT  TACACS+  Should work through NAT systems 23 7/14 IS 3200, Summer 2010

Password Security Issues  Passwords that can be cracked (accessed by an unauthorized user)  Password vulnerabilities  Lax security habits 24 7/14 IS 3200, Summer 2010

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 25 7/14 IS 3200, Summer 2010

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 26 7/14 IS 3200, Summer 2010

Lax Security Habits  To maintain some level of integrity, draw up a formal Memorandum of Understanding (MOU) 27 7/14 IS 3200, Summer 2010

Password Security Tools  One-time password software  Shadow password system 28 7/14 IS 3200, Summer 2010

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 29 7/14 IS 3200, Summer 2010

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 30 7/14 IS 3200, Summer 2010

Other Authentication Systems  Single-password systems  One-time password systems  Certificate-based authentication  802.1x Wi-Fi authentication 31 7/14 IS 3200, Summer 2010

Single-Password Systems  Operating system password  Internal firewall password 32 7/14 IS 3200, Summer 2010

One-Time Password Systems  Single Key (S/Key)  SecurID  Axent Pathways Defender 33 7/14 IS 3200, Summer 2010

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 34 7/14 IS 3200, Summer 2010

SecurID  Uses two-factor authentication  Physical object  Piece of knowledge  Most frequently used one-time password solution with FireWall /14 IS 3200, Summer 2010

SecurID Tokens 36 7/14 IS 3200, Summer 2010

Axent Pathways Defender  Uses two-factor authentication and a challenge-response system 37 7/14 IS 3200, Summer 2010

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 38 7/14 IS 3200, Summer 2010

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) 39 7/14 IS 3200, Summer 2010

Wireless Authentication 40 7/14 IS 3200, Summer 2010

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 41 7/14 IS 3200, Summer 2010

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 42 7/14 IS 3200, Summer 2010

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 43 7/14 IS 3200, Summer 2010

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 multiple-word password 44 7/14 IS 3200, Summer 2010