Practical Unix and Internet Security ^{2nd Ed.}

When Practical UNIX Security was first published in 1991, it became an instant classic. Crammed with information about host security, it saved many a UNIX system administrator and user from disaster.

This second edition is a complete rewrite of the original book. It's packed with twice the pages and offers even more practical information for UNIX users and administrators. You'll find coverage of features of many types of UNIX systems, including SunOS, Solaris, BSDI, AIX, HP-UX, Digital UNIX, and Linux. The first edition was practical, entertaining, and full of useful scripts, tips, and warnings. This edition is all those things — and more.

Practical UNIX and Internet Security includes detailed coverage of Internet security and networking issues, including World Wide Web security, wrapper and proxy programs, integrity management tools, secure programming, and how to secure TCP/IP services (e.g., FTP, SMTP, DNS). Chapters on host security contain up-to-date details on passwords, the UNIX filesystem, cryptography, backups, logging, physical security, telephone security, UUCP, firewalls, and dealing with breakins. You'll also find extensive summary appendixes on freely available security tools, references, and security-related organizations.

Practical UNIX and Internet Security is the authoritative book covering every aspect of computer security on UNIX machines and the Internet. Don't even think of running a system without it!

1. Computer Security Basics
1. Introduction
• What is Computer Security?
• What is an Operating System?
• History of UNIX
• Security and UNIX
• Role of the Book
2. Policies and Guidelines
• Planning Your Security Needs
• Risk Assessment
• Cost-Benefit Analysis
• Policy
• The Problem with Security Through Obscurity
2. User Responsibility
3. Users and Passwords
• Usernames
• Passwords
• Entering Your Password
• Changing Your Password
• Verifying Your New Password
• The Care and Feeding of Passwords
• One-Time Passwords
• Summary
4. Users, Groups, and the Superuser
• Users and Groups
• Special Usernames
• su: Changing Who You Claim to Be
• Summary
5. The UNIX Filesystem
• Files,
• Using File Permissions
• The umask
• Using Directory Permissions
• SUID
• Device Files
• chown: Changing a File's Owner
• chgrp: Changing a File's Group
• Oddities and Dubious Ideas
• Summary
6. Cryptography
• A Brief History of Cryptography
• What Is Encryption?
• The Enigma Encryption System
• Common Cryptographic Algorithms
• Message Digests and Digital Signatures
• Encryption Programs Available for UNIX
• des: The Data Encryption Standard
• Encryption and U.S. Law
3. System Security
7. Backups
• Make Backups!
• Sample Backup Strategies
• Backing Up System Files
• Software for Backups
8. Defending Your Accounts
• Dangerous Accounts
• Monitoring File Format
• Restricting Logins
• Managing Dormant Accounts
• Protecting the root Account
• The UNIX Encrypted Password System
• One-Time Passwords
• Administrative Techniques for Conventional Passwords
9. Integrity Management
• Prevention
• Detecting Change
• A Final Note
10. Auditing and Logging
• The Basic Log Files
• The acct/pacct Process Accounting File
• Program-Specific Log Files
• Per-User Trails in the Filesystem
• The UNIX System Log (syslog) Facility
• Swatch: A Log File Tool
• Handwritten Logs
• Managing Log Files
11. Protecting Against Programmed Threats
• Programmed Threats: Definitions
• Damage
• Authors
• Entry
• Protecting Yourself
• Protecting Your System
12. Physical Security
• One Forgotten Threat
• Protecting Computer Hardware
• Protecting Data
• Story: A Failed Site Inspection
13. Personnel Security
• Background Checks
• On the Job
• Outsiders
4. Network and Internet Security
14. Telephone Security
• Modems: Theory of Operations
• Serial Interfaces
• The RS-232 Serial Protocol
• Modems and Security
• Modems and UNIX
• Additional Security for Modems
15. UUCP
• About UUCP
• Versions of UUCP
• Security in Version 2 UUCP
• Security in BNU UUCP
• Additional Security Concerns
• Early Security Problems with UUCP
• UUCP Over Networks
• Summary
16. TCP/IP Networks
• Networking
• IPv4: The Internet Protocol Verion 4
• IP Security
• Other Network Protocols
• Summary
17. TCP/IP Services
• Understanding UNIX Internet Servers
• Controlling Access to Servers
• Primary UNIX Network Services
• Security Implications of Network Services
• Monitoring Your Network with netstat
• Network Scanning
• Summary
18. WWW Security
• Security and the World Wide Web
• Running a Secure Server
• Controlling Access to Files on Your Server
• Avoiding Risks of Eavesdropping
• Risks of Web Browsers
• Dependence on Third Parties
• Summary
19. RPC, NIS, NIS+, and Kerberos
• Securing Network Services
• Sun's Remote Procedure Call (RPC)
• Secure RPC (AUTH_DES)
• Sun's Network Information Service (NIS)
• Sun's NIS+
• Kerberos
• Other Network Authentication Systems
20. NFS
• Understanding NFS
• Server-Side NFS Security
• Client-Side NFS Security
• Improving NFS Security
• Some Last Comments
5. Advanced Topics
21. Firewalls
• What's a Firewall?
• Building Your Own Firewall
• Example: Cisco Systems Routers as Chokes
• Setting Up the Gate
• Special Considerations
• Final Comments
22. Wrappers and Proxies
• Why Wrappers?
• sendmail (smap/smapd) Wrapper
• tcpwrapper
• SOCKS
• UDP Relayer
• Writing Your Own Wrappers
23. Writing Secure SUID and Network Programs
• One Bug Can Ruin Your Whole Day
• Tips on Writing Network Programs
• Tips on Writing SUID/SGID Programs
• Tips on Using Passwords
• Tips on Generation Random Numbers
6. Handling Security Incidents
24. Discovering a Break-in
• Prelude
• Discovering an Intruder
• The Log Files: Discovering an Intruder's Tracks
• Cleaning Up After the Intruder
• An Example
• Resuming Operations
• Damage Control
25. Denial of Service Attacks and Solutions
• Destructive Attacks
• Overload Attacks
• Network Denial of Service Attacks
26. Computer Security and U.S. Law
• Legal Options After a Break-in
• Criminal Prosecution
• Civil Actions
• Other Liability
27. Who Do You Trust?
• Can You Trust Your Computer?
• Can You Trust Your Suppliers?
• Can You Trust People?
• What All This Means
7. Appendixes
1. UNIX Security Checklist
2. Important Files
• Security-Related Devices aand Files
• Important Files in Your Home Directory
• SUID and SGID Files
3. UNIX Processes
• About Processes
• Creating Processes
• Signals
• The kill Command
• Starting Up UNIX and Logging In
4. Paper Sources
• UNIX Security References
• Other Computer References
• Security Periodicals
5. Electronic Resources
• Mailing Lists
• Usenet Groups
• WWW Pages
• Software Resources
6. Organizations
• Professional Organizations
• U.S. Government Organizations
• Emergency Response Organizations
7. Table of IP Services

The classical text has been updated. Keep it in your bookshelf.