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TextFile

"Practical Unix Security"
by Simson Garfinkel and Eugene Spafford
O'Reilly & Associates (the Nutshell Handbook people).
Approx 480 pages, 1991, $29.95.
ISBN 0-937175-72-2

Quotes from reviewers:

Cliff Stoll:
   Worried about who's in your Unix system?  
   Losing sleep because someone might be messing with your computer?   
   Having headaches from obscure computer manuals?

   Then _Practical_Unix_Security_ is for you.  

   This handy book tells you where the holes are and how to cork 'em up.  
   Moreover, you'll learn about how Unix security really works.
   Spafford and Garfinkel show you how to tighten up your Unix system
   without pain.  No secrets here -- just solid computing advice.

   Buy this book and save on aspirin.

Tom Christiansen, Convex Computer Corp:
   This book is the first I've seen that actually seemed to 
   address the many security issues that I keep around on 
   my own little list, and it did so well.

Paul Clark, Trusted Information Systems:
   The book could easily become a standard desktop reference for 
   anyone involved in system administration. In general, its 
   comprehensive treatment of Unix security issues
   will enlighten anyone with an interest in the topic.

Matt Bishop, Dartmouth 
   ...I liked the book; it covers a lot of material not
   normally covered and provides practical instructions on how to do
   things.  This will be very useful for practitioners...This book is
   far superior to any other I have seen on UNIX security.

Laurie Sefton, Apple:
   Finally there is a UNIX security book that covers the BSD world as
   well as the SYS V version...The other aspect of UNIX security books
   that has been sorely lacking was the "rest of UNIX" security.  All the
   other books had a very thin overview of "down and dirty" security, as
   if they were afraid of giving out too much information...As soon as
   this is out, I'm ordering copies for all my people, and extra copies
   for the library at Apple.


Orders:  800-338-6887 (US & Canada)
	 707-829-0515 (Europe)
	 nuts@ora.com (e-mail)


Preliminary Table of Contents:

Preface  
    Scope of this Book
    Which UNIX System?
    Conventions Used in this Book
    Acknowledgments
    Three Final Notes

Chapter 1  Introduction  
    What's Computer Security?
    What's an Operating System?
    History of UNIX
    Security and UNIX
    Security and Networks
    Types of Security
        Risk Assessment
        Assessing Your Risk
        Reacting to an Emergency
        Other Important Steps
    The Problem with Security Through Obscurity
    The First Step

Chapter 2  Users and Passwords  
    Usernames
        The /etc/passwd File
        The /etc/passwd File and Network Databases
    Passwords
        Why Use Passwords?
        Entering Your Password
        Changing Your Password
        Checking Out Your New Password
    UNIX'S Encrypted Password System
        The crypt() Algorithm
        What is Salt?
    The Care and Feeding of Passwords
    Bad Passwords:  Open Doors
    Good Passwords:  Locked Doors
        Passwords on Multiple Machines
        Writing Down Passwords
    Administrative Techniques
        Assigning Passwords to Users
        Password Generators
        Shadow Password Files
        Password Aging and Expiration
        Algorithm Changes
        Preventing Direct Logins to Accounts
        Account Names Revisited
    Summary

Chapter 3  Users, Groups, and the Superuser  
    Users and Groups
        User Identifiers (UIDs)
        Groups and Group Identifiers (GIDs)
    Special Users
        The Superuser
        Other Special Users
        Impact of the /etc/passwd and /etc/group Files on Security
    The su(1) Command:  Changing Who You Are
        Becoming the Superuser
        Restricting su
        The Bad su Log
        Other Uses of su
        Summary

Chapter 4  The UNIX File System  
    Files
        Using the ls(1) command
        Understanding File Permissions
        File Permissions in Detail
    Using File Permissions
        chmod:  Changing a File's Permissions
        Setting a File's Permissions
        Calculating Octal File Permissions
        Using Octal File Permissions
    The umask
        The umask command
        Common umask Values
    Using Directory Permissions
    SUID
        SUID, SGID, and Sticky Bits
        Problems With SUID
        Finding All of the SUID and SGID Files
        Turning off SUID and SGID in Mounted File Systems
        SGID and Sticky Bits on Directories 
		(Berkeley UNIX and Sun OS Only)
        SGID Bit on Files (System V UNIX only)
    chown:  Changing a File's Owner
    chgrp:  Changing a File's Group

Chapter 5  Defending Your Accounts  
    Dangerous Accounts
        Accounts Without Passwords
        Default Accounts
        Accounts That Run a Single Command
        Open Accounts
    Group Accounts
    Dormant Accounts
        Changing an Account's Password
        Changing the Account's Login Shell
        Finding Dormant Accounts
    Protecting the Root Account Under Berkeley UNIX
        Secure Terminals
        The wheel Group

Chapter 6  Securing Your Data  
    File Backups
        Why Make Backups?
        What Should You Back up?
        Kinds of Backups
        How Long Should You Keep a Backup?
        Security for Backups
    Database Backups and Daily Checking
    Integrity Checking and Checklists
        Checklists
        File Protection Modes
        Read-Only Disks
        Comparison Copies
        Checklists
        Signatures

Chapter 7  The UNIX Log Files  
    The /usr/adm/lastlog File
    The /etc/utmp and /usr/adm/wtmp Files
        Last Program
        Pruning the wtmp File
    The /usr/adm/acct File
    The Berkeley System Log (syslog) Facility
        The syslog.conf Configuration File
        Where To Log

Chapter 8  Protecting Against Programmed Threats  
    Programmed Threats:  Definitions
        Back Doors and Trap Doors
        Logic Bombs
        Viruses
        Worms
        Trojan Horses
        Bacteria and Rabbits
    Damage
    Authors
    Entry
    Protecting Yourself
        Shell Features
        Startup File Attacks
        Abusing Automatic Mechanisms
        Unexpected Interactions
    Protecting Your System
        File Protections
        SUID and SGID Programs
        Notes on Writing a SUID Program
        SUID Shell Scripts

Chapter 9  Modems  
    Theory of Operation
    Serial Interfaces
        The RS-232 Serial Protocol
        Originate and Answer
        Modems and Security
    Modems and UNIX
        Hooking Up a Modem to Your Computer
        Setting Up the UNIX Device
        Checking Your Modem
        Physical Protection
    Additional Security for Modems

Chapter 10  UUCP  
    About UUCP
        The uucp Command
        The uux Command
        The mail Command
        How The uucp Commands Work
    Versions of UUCP
    UUCP and Security
        Assigning Additional UUCP Logins
        Establishing UUCP Passwords
        Security of the L.sys and Systems Files
    Security in Version 2 UUCP
        USERFILE:  Providing Remote File Access
        A USERFILE Example
        L.cmds:  Providing Remote Command Execution
    Security in BNU UUCP
        The Permissions File
        Permissions Commands
        uucheck(1):  Checking Your Permissions File
    Additional Security Concerns
        Mail Forwarding for UUCP
        Automatic Execution of Cleanup Scripts
    Early Security Problems with UUCP
        Summary

Chapter 11  Networks and Security  
    The Internet
    Internet Addresses
        The /etc/hosts File
        Network Hostname Service
    Clients and Servers
        TCP/IP
        UDP/IP
        UNIX Network Servers
        The /etc/services File
        Starting the Servers
        The /etc/inetd Program
    Network Services
        TELNET
        rlogin and rsh
        rexec
        finger
        Electronic Mail
        FTP
        TFTP
        The X Window System
    Security Implications of Network Services
        Monitoring Your Network with netstat
        Summary

Chapter 12  Sun's NFS  
    NIS
        Netgroups
        Setting up Netgroups
    NFS
        How NFS Works
        The /etc/exports File
        The showmount Command
        Authentication and NFS
    Improving Basic NFS Security
        Limiting Exported File Systems
        Limit Exported Machines
        Use Root Ownership
        Export Read-only
        Do Not Export Server Executables
        The fsirand Program
        Summary:  Security Implications of NFS

Chapter 13  Kerberos and Secure RPC  
    The Problem
        What's Wrong with LANs?
        Minimizing the Problems
    MIT's Kerberos
        What's It Like to Use Kerberos?
        How to Install Kerberos
        What's Wrong with Kerberos?
    Sun Microsystems' Secure RPC
        How Secure RPC Works
        What's It Like to Use Secure NFS?
        How to Install Secure RPC
        What's Wrong with Secure RPC?

Chapter 14  Firewall Machines  
    What's a Firewall?
        Internal Firewalls
        External Firewalls
    Setting Up a Firewall
        The Choke
        Choosing the Choke's Protocols
    Setting up the Gate
        Name Service
        Electronic Mail
        Netnews
        FTP
        Other Services
    An Alternate Method
    Special Considerations

Chapter 15  Discovering a Break-in  
    Prelude
    Discovering an Intruder
        Catching One in the Act
        What to Do When You Catch Somebody
        Tracing a Connection
        Getting Rid of the Intruder
    The Log Files:  Discovering an Intruder's Tracks
    Cleaning Up After the Intruder
        New Accounts
    An Example
    A Last Note:  Never Trust Anything Except Hard Copy

Chapter 16  Denial of Service Attacks and Solutions  
    Destruction Attacks
    Overload Attacks
        Process Overload Attacks
        Disk Attacks
        Swap Space Attacks
        Soft Process Limits:  Preventing Accidental
		 Denial of Service
    Network Denial of Service Attacks
        Service Overloading
        Message Flooding
        Signal Grounding

Chapter 17  Computer Security and the U.S. Law  
    Legal Options After a Break-in
    Criminal Prosecution
        The Local Option
        Federal Jurisdiction
        Federal Computer Crime Laws
        Hazards of Criminal Prosecution
        If You or One of Your Employees is a 
		Target of an Investigation
        Other Tips
    Civil Actions
    Privacy and The Electronic Communications Privacy Act

Chapter 18  Encryption  
    Who Needs Encryption?
    Cryptographic Strength
    Types of Encryption Systems
    ROT13
    crypt
        Enigma
        UNIX crypt
        Ways of Improving the Security of crypt
        Example
    The Data Encryption Standard (DES)
        DES Modes
        Use and Export of DES
        DES Strength
        Sun's des command
    RSA and Public Key Cryptography
        How RSA Works
        An RSA Example
        Strength of RSA
    Proprietary Encryption Systems
    Protect Your Key!

Chapter 19  Physical Security  
    Protecting Computer Hardware
        The Environment
        Accidents
        Physical Access
        Vandalism
        Acts of War and Terrorism
        Theft
        Related Concerns
    Protecting Data
        Eavesdropping
        Backups
        Local Storage
        Unattended Terminals

Appendix A  UNIX Security Checklist 

Appendix B  Important Files  
    System Files
    Important Files in your Home Directory
    SUID Files in Berkeley UNIX
    SGID Files in Berkeley UNIX
    SUID Files in System V R3.2 UNIX
    SGID Files in System V UNIX

Appendix C  UNIX Processes  
    Processes
        Processes and Programs
        The ps Command
        Process Properties
    Creating Processes
    Signals
    The kill Command
    Starting Up UNIX and Logging In
        Process #1: /etc/init
        Letting Users Log In
        Running the User's Shell

Appendix D  How Kerberos Works  
    Kerberos's Parts
    Using Kerberos
    Using a Service

Appendix E  Other Sources  
    References
       General Computer Security
       UNIX Security
       Computer Viruses and Programmed Threats
       Computer Crime and Law
       Understanding the Computer Security 'Culture'
       Understanding and Using Networks
       Using and Programming UNIX
       Security Products and Services Information
       Miscellaneous References
    Organizations
        Association for Computing Machinery (ACM)
        IEEE Computer Society
        ASIS
        Computer Security Institute (CSI)
        NIST
        Computer Emergency Response Team (CERT)
        DOE's Computer Incident Advisory Capability (CIAC)
    Software Resources
        Getting Kerberos
        Getting COPS