Practical UNIX and Internet Security. 3rd Edition

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• Practical Unix & Internet Security, 3rd Edition
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  • A Note Regarding Supplemental Files
  • Preface
    • Unix Security?
      • What This Book Is
      • What This Book Is Not
      • Third-Party Security Tools
    • Scope of This Book
    • Which Unix System?
      • Versions Covered in This Book
      • Secure Versions of Unix
    • Conventions Used in This Book
    • Comments and Questions
    • Acknowledgments
      • Third Edition
      • Second Edition
      • First Edition
    • A Note to Would-Be Attackers
  • I. Computer Security Basics
    • 1. Introduction: Some Fundamental Questions
      • What Is Computer Security?
      • What Is an Operating System?
      • What Is a Deployment Environment?
      • Summary
    • 2. Unix History and Lineage
      • History of Unix
        • Multics: The Unix Prototype
        • The Birth of Unix
          • Unix escapes AT&T
          • Unix goes commercial
          • The Unix Wars: Why Berkeley 4.2 over System V
          • Unix Wars 2: SVR4 versus OSF/1
        • Free Unix
          • FSF and GNU
          • Minix
          • Xinu
          • Linux
          • NetBSD, FreeBSD, and OpenBSD
          • Businesses adopt Unix
        • Second-Generation Commercial Unix Systems
        • What the Future Holds
      • Security and Unix
        • Expectations
        • Software Quality
        • Add-on Functionality Breeds Problems
        • The Failed P1003.1e/2c Unix Security Standard
      • Role of This Book
      • Summary
    • 3. Policies and Guidelines
      • Planning Your Security Needs
        • Types of Security
        • Trust
      • Risk Assessment
        • Steps in Risk Assessment
          • Identifying assets
          • Identifying threats
        • Review Your Risks
      • Cost-Benefit Analysis and Best Practices
        • The Cost of Loss
        • The Probability of a Loss
        • The Cost of Prevention
        • Adding Up the Numbers
        • Best Practices
        • Convincing Management
      • Policy
        • The Role of Policy
        • Standards
        • Guidelines
        • Some Key Ideas in Developing a Workable Policy
          • Assign an owner
          • Be positive
          • Remember that employees are people too
          • Concentrate on education
          • Have authority commensurate with responsibility
          • Be sure you know your security perimeter
          • Pick a basic philosophy
          • Defend in depth
        • Risk Management Means Common Sense
      • Compliance Audits
      • Outsourcing Options
        • Formulating Your Plan of Action
        • Choosing a Vendor
          • Get a referral and insist on references
          • Beware of soup-to-nuts
          • Insist on breadth of background
          • People
          • Reformed hackers
        • Monitoring Services
        • Final Words on Outsourcing
      • The Problem with Security Through Obscurity
        • Keeping Secrets
        • Responsible Disclosure
      • Summary
  • II. Security Building Blocks
    • 4. Users, Passwords, and Authentication
      • Logging in with Usernames and Passwords
        • Unix Usernames
        • Authenticating Users
        • Authenticating with Passwords
          • Entering your password
          • Changing your password
          • Verifying your new password
          • Changing another users password
      • The Care and Feeding of Passwords
        • Bad Passwords: Open Doors
        • Smoking Joes
        • Good Passwords: Locked Doors
        • Password Synchronization: Using the Same Password on Many Machines
        • Writing Down Passwords
      • How Unix Implements Passwords
        • The /etc/passwd File
        • The Unix Encrypted Password System
          • The traditional crypt ( ) algorithm
          • Unix salt
          • crypt16( ), DES Extended, and Modular Crypt Format
          • The shadow password and master password files
        • One-Time Passwords
        • Public Key Authentication
      • Network Account and Authorization Systems
        • Using Network Authorization Systems
        • Viewing Accounts in the Network Database
          • NIS and NIS+
          • Kerboros DCE
          • NetInfo
          • RADIUS
          • LDAP
      • Pluggable Authentication Modules (PAM)
      • Summary
    • 5. Users, Groups, and the Superuser
      • Users and Groups
        • The /etc/passwd File
        • User Identifiers (UIDs)
        • Groups and Group Identifiers (GIDs)
          • The /etc/group file
      • The Superuser (root)
        • What the Superuser Can Do
        • What the Superuser Cant Do
        • Any Username Can Be a Superuser
        • The Problem with the Superuser
      • The su Command: Changing Who You Claim to Be
        • Real and Effective UIDs with the su Command
          • Saved IDs
          • Other IDs
        • Becoming the Superuser
        • Use su with Caution
        • Using su to Run Commands from Scripts
        • Restricting su
        • The su Log
          • The sulog under Solaris
          • The sulog under Berkeley Unix
          • The sulog under Red Hat Linux
          • Final caution
        • sudo: A More Restrictive su
      • Restrictions on the Superuser
        • Secure Terminals: Limiting Where the Superuser Can Log In
        • BSD Kernel Security Levels
        • Linux Capabilities
      • Summary
    • 6. Filesystems and Security
      • Understanding Filesystems
        • UFS and the Fast File System
          • File contents
          • Inodes
          • Directories and links
        • The Virtual Filesystem Interface
        • Current Directory and Paths
      • File Attributes and Permissions
        • Exploring with the ls Command
        • File Times
        • File Permissions
          • A file permissions example
        • Directory Permissions
      • chmod: Changing a Files Permissions
        • Setting a Files Permissions
          • Calculating octal file permissions
          • Using octal file permissions
        • Access Control Lists
      • The umask
        • The umask Command
        • Common umask Values
      • SUID and SGID
        • Sticky Bits
        • SGID and Sticky Bits on Directories
        • SGID Bit on Files (System V-Derived Unix Only): Mandatory Record Locking
        • Problems with SUID
        • SUID Scripts
          • An example of a SUID attack: IFS and the /usr/lib/preserve hole
        • Finding All of the SUID and SGID Files
          • The Solaris ncheck command
        • Turning Off SUID and SGID in Mounted Filesystems
      • Device Files
        • Unauthorized Device Files
      • Changing a Files Owner or Group
        • chown: Changing a Files Owner
          • Old and new chown behavior
          • Use chown with caution
        • chgrp: Changing a Files Group
      • Summary
    • 7. Cryptography Basics
      • Understanding Cryptography
        • Roots of Cryptography
        • Cryptography as a Dual-Use Technology
        • A Cryptographic Example
        • Cryptographic Algorithms and Functions
      • Symmetric Key Algorithms
        • Cryptographic Strength of Symmetric Algorithms
        • Key Length with Symmetric Key Algorithms
        • Common Symmetric Key Algorithms
        • Attacks on Symmetric Encryption Algorithms
          • Key search (brute force) attacks
          • Cryptanalysis
          • Systems-based attacks
      • Public Key Algorithms
        • Uses for Public Key Encryption
          • Encrypted messaging
          • Digital signatures
        • Attacks on Public Key Algorithms
          • Key search attacks
          • Analytic attacks
          • Known versus published methods
      • Message Digest Functions
        • Message Digest Algorithms at Work
        • Uses of Message Digest Functions
        • HMAC
        • Attacks on Message Digest Functions
      • Summary
    • 8. Physical Security for Servers
      • Planning for the Forgotten Threats
        • The Physical Security Plan
        • The Disaster Recovery Plan
        • Other Contingencies
      • Protecting Computer Hardware
        • Protecting Against Environmental Dangers
          • Fire
          • Smoke
          • Dust
          • Earthquakes
          • Explosions
          • Extreme temperatures
          • Bugs (biological)
          • Electrical noise
          • Lightning
          • Vibration
          • Humidity
          • Water
          • Environmental monitoring
        • Preventing Accidents
          • Food and drink
        • Controlling Physical Access
          • Raised floors and dropped ceilings
          • Entrance through air ducts
          • Glass walls
        • Defending Against Vandalism
          • Ventilation holes
          • Network cables
          • Network connectors
          • Utility connections
        • Defending Against Acts of War and Terrorism
      • Preventing Theft
        • Understanding Computer Theft
        • Laptops and Portable Computers
          • Locks
          • Tagging
        • Laptop Recovery Software and Services
        • RAM Theft
        • Encryption
      • Protecting Your Data
        • Eavesdropping
          • Wiretapping
          • Eavesdropping over local area networks (Ethernet and twisted pairs)
          • Eavesdropping on 802.11 wireless LANs
          • Eavesdropping by radio and using TEMPEST
          • Fiber optic cable
          • Keyboard monitors
        • Protecting Backups
          • Verify your backups
          • Protect your backups
        • Sanitizing Media Before Disposal
        • Sanitizing Printed Media
        • Protecting Local Storage
          • Printer buffers
          • Printer output
          • X terminals
          • Function keys
        • Unattended Terminals
          • Built-in shell autologout
          • Screensavers
        • Key Switches
      • Story: A Failed Site Inspection
        • What We Found
          • Fire hazards
          • Potential for eavesdropping and data theft
          • Easy pickings
          • Physical access to critical computers
          • Possibilities for sabotage
        • Nothing to Lose?
      • Summary
    • 9. Personnel Security
      • Background Checks
        • Intensive Investigations
        • Rechecks
      • On the Job
        • Initial Training
        • Ongoing Training and Awareness
        • Performance Reviews and Monitoring
        • Auditing Access
        • Least Privilege and Separation of Duties
      • Departure
      • Other People
      • Summary
  • III. Network and Internet Security
    • 10. Modems and Dialup Security
      • Modems: Theory of Operation
        • Serial Interfaces
        • The RS-232 Serial Protocol
        • Originate and Answer
        • Baud and bps
      • Modems and Security
        • Banners
        • Caller-ID and Automatic Number Identification
        • One-Way Phone Lines
        • Protecting Against Eavesdropping
          • Kinds of eavesdropping
          • Eavesdropping countermeasures
        • Managing Unauthorized Modems with Telephone Scanning and Telephone Firewalls
          • Telephone scanning
          • Telephone firewalls
          • Limitations of scanning and firewalls
      • Modems and Unix
        • Connecting a Modem to Your Computer
        • Setting Up the Unix Device
        • Checking Your Modem
          • Originate testing
          • Answer testing
          • Privilege testing
        • Protection of Modems and Lines
      • Additional Security for Modems
      • Summary
    • 11. TCP/IP Networks
      • Networking
        • The Internet
          • Todays Internet
          • Whos on the Internet?
        • Networking and Unix
      • IP: The Internet Protocol
        • Internet Addresses
          • IP networks
          • Classical network addresses
          • CIDR addresses
        • Routing
        • Hostnames
          • Format of the hostname
          • The /etc/hosts file
        • Packets and Protocols
          • ICMP
          • TCP
          • UDP
        • Clients and Servers
        • Name Service
          • DNS under Unix
          • Other naming services
      • IP Security
        • Using Encryption to Protect IP Networks from Eavesdropping
        • Hardening Against Attacks
        • Firewalls and Physical Isolation
        • Improving Authentication
          • Authentication and DNS
          • Authentication and email
          • April Fools! authentication and Netnews
          • Adding authentication to TCP/IP with ident
        • Decoy Systems
      • Summary
    • 12. Securing TCP and UDP Services
      • Understanding Unix Internet Servers and Services
        • The /etc/services File
          • Calling getservbyname( )
          • Ports cannot be trusted
        • Starting the Servers
          • Startup on different Unix systems
          • Startup examples
        • The inetd Program
      • Controlling Access to Servers
        • Access Control Lists with TCP Wrappers
          • What TCP Wrappers does
          • The TCP Wrappers configuration language
          • Making sense of your TCP Wrappers configuration files
        • Using a Host-Based Packet Firewall
          • The ipfw host-based firewall
          • An ipfw example
      • Primary Unix Network Services
        • echo and chargen (TCP and UDP Ports 7 and 19)
        • systat (TCP Port 11)
        • FTP: File Transfer Protocol (TCP Ports 20 and 21)
          • Anonymous FTP
          • FTP active mode
          • FTP passive mode
          • Setting up an FTP server
          • Restricting FTP with the standard Berkeley FTP server
          • Setting up anonymous FTP with the standard Unix FTP server
          • Allowing only FTP access
        • SSH: The Secure Shell (TCP Port 22)
          • Host authentication with SSH
          • Client authentication with SSH
        • Telnet (TCP Port 23)
        • SMTP: Simple Mail Transfer Protocol (TCP Port 25)
          • Configuration files
          • Security concerns with SMTP banners and commands
          • SMTP relaying and bulk email (a.k.a. spam)
          • Overflowing system mailboxes
          • Delivery to programs
          • Overall security of Berkeley sendmail versus other MTAs
        • TACACS and TACACS+ (UDP Port 49)
        • Domain Name System (DNS) (TCP and UDP Port 53)
          • DNS zone transfers
          • DNS nameserver attacks
          • DNSSEC
          • DNS best practices
        • BOOTP: Bootstrap Protocol, and DHCP: Dynamic Host Configuration Protocol (UDP Ports 67 and 68)
        • TFTP: Trivial File Transfer Protocol (UDP Port 69)
        • finger (TCP Port 79)
          • The .plan and .project files
          • Disabling finger
        • HTTP, HTTPS: HyperText Transfer Protocol (TCP Ports 80, 443)
        • POP, POPS: Post Office Protocol, and IMAP, IMAPS: Internet Message Access Protocol (TCP Ports 109, 110, 143, 993, 995)
        • Sun RPCs portmapper (UDP and TCP Ports 111)
        • Identification Protocol (TCP Port 113)
        • NNTP: Network News Transport Protocol (TCP Port 119)
        • NTP: Network Time Protocol (UDP Port 123)
          • Sudden changes in time
          • An NTP example
        • SNMP: Simple Network Management Protocol (UDP Ports 161 and 162)
        • rexec (TCP Port 512)
        • rlogin and rsh (TCP Ports 513 and 514)
          • Trusted hosts and users
          • Specifying trusted hosts with /etc/hosts.equiv and ~/.rhosts
          • /etc/hosts.lpd file
        • RIP Routed: Routing Internet Protocol (UDP Port 520)
        • The X Window System (TCP Ports 6000-6063)
          • /etc/logindevperm
          • X security
          • The xhost facility
          • Using Xauthority magic cookies
          • Tunneling X with SSH
        • RPC rpc.rexd (TCP Port 512)
        • Communicating with MUDs, Internet Relay Chat (IRC), and Instant Messaging
      • Managing Services Securely
        • Monitoring Your Host with netstat
          • Limitation of netstat and lsof
        • Monitoring Your Network with tcpdump
        • Network Scanning
      • Putting It All Together: An Example
      • Summary
    • 13. Sun RPC
      • Remote Procedure Call (RPC)
        • Suns portmap/rpcbind
        • RPC Authentication
          • AUTH_NONE
          • AUTH_UNIX
          • AUTH_DES
          • AUTH_KERB
      • Secure RPC (AUTH_DES)
        • Secure RPC Authentication
          • Proving your identity
          • Using Secure RPC services
          • Setting the window
        • Setting Up Secure RPC with NIS
          • Creating passwords for users
          • Creating passwords for hosts
          • Making sure Secure RPC support is running on every workstation
        • Using Secure RPC
        • Limitations of Secure RPC
      • Summary
    • 14. Network-Based Authentication Systems
      • Suns Network Information Service (NIS)
        • NIS Fundamentals
          • Including or excluding specific accounts
          • Importing accounts without really importing accounts
        • NIS Domains
        • NIS Netgroups
          • Setting up netgroups
          • Using netgroups to limit the importing of accounts
          • Limitations of NIS
          • Spoofing RPC
          • Spoofing NIS
          • NIS is confused about +
        • Unintended Disclosure of Site Information with NIS
      • Suns NIS+
        • What NIS+ Does
        • NIS+ Tables and Other Objects
        • Using NIS+
          • Changing your password
          • When a users passwords dont match
        • NIS+ Limitations
      • Kerberos
        • Kerberos Authentication
          • Initial login
          • Using the ticket-granting ticket
          • Authentication, data integrity, and secrecy
          • Kerberos 4 versus Kerberos 5
        • Getting Kerberos
        • Using Kerberos
        • Kerberos Limitations
      • LDAP
        • LDAP: The Protocol
        • LDAP Integrity and Reliability
        • Authentication with LDAP
          • nss_ldap
          • pam_ldap
        • Configuring Authentication with nss_ldap
          • Setting up the LDAP server
          • Setting up the LDAP clients
      • Other Network Authentication Systems
        • DCE
        • SESAME
      • Summary
    • 15. Network Filesystems
      • Understanding NFS
        • NFS History
        • File Handles
        • The MOUNT Protocol
        • The NFS Protocol
          • How NFS creates a reliable filesystem from a best-effort protocol
          • Hard, soft, and spongy mounts
          • Connectionless and stateless
          • NFS and root
        • NFS Version 3
      • Server-Side NFS Security
        • Limiting Client Access: /etc/exports and /etc/dfs/dfstab
          • /etc/exports
          • /usr/etc/exportfs
          • Exporting NFS directories under System V: share and dfstab
        • The showmount Command
      • Client-Side NFS Security
      • Improving NFS Security
        • Limit Exported and Mounted Filesystems
          • The example explained
        • Export Read-Only
        • Use Root Ownership
        • Remove Group-Write Permission for Files and Directories
        • Do Not Export Server Executables
        • Do Not Export Home Directories
        • Do Not Allow Users to Log into the Server
        • Use fsirand
        • Set the portmon Variable
        • Use showmount -e
        • Use Secure NFS
      • Some Last Comments on NFS
        • Well-Known Bugs
        • For Real Security, Dont Use NFS
      • Understanding SMB
        • SMB History
        • Protocols
          • Name service
          • Authentication
          • File access
        • Configuring the Samba Server
        • Samba Server Security
          • Connecting to the server
          • User authentication
          • Authorization
          • Data integrity and privacy
        • Samba Client Security
        • Improving Samba Security
      • Summary
    • 16. Secure Programming Techniques
      • One Bug Can Ruin Your Whole Day . . .
        • The Lesson of the Internet Worm
        • An Empirical Study of the Reliability of Unix Utilities
          • What he found
          • Wheres the beef?
      • Tips on Avoiding Security-Related Bugs
        • Design Principles
        • Coding Standards
        • Things to Avoid
        • Before You Finish
      • Tips on Writing Network Programs
        • Things to Do
        • Things to Avoid
      • Tips on Writing SUID/SGID Programs
      • Using chroot( )
      • Tips on Using Passwords
      • Tips on Generating Random Numbers
        • Unix Pseudorandom Functions
          • rand( )
          • random( )
          • drand48( ), lrand48( ), and mrand48( )
        • Picking a Random Seed
        • A Good Random Seed Generator
      • Summary
  • IV. Secure Operations
    • 17. Keeping Up to Date
      • Software Management Systems
        • Package-Based Systems
        • Source-Based Systems
          • Source code and patches
          • CVS
      • Updating System Software
        • Learning About Patches
        • Upgrading Distributed Applications
        • Sensitive Upgrades
      • Summary
    • 18. Backups
      • Why Make Backups?
        • The Role of Backups
        • What Should You Back Up?
        • Types of Backups
        • Guarding Against Media Failure
          • Replace tapes as needed
          • Keep your tape drives clean
          • Verify the backup
        • How Long Should You Keep a Backup?
        • Security for Backups
          • Physical security for backups
          • Write-protect your backups
          • Data security for backups
        • Legal Issues
        • Deciding Upon a Backup Strategy
        • Individual Workstation
          • Backup plan
          • Retention schedule
        • Small Network of Workstations and a Server
          • Backup plan
          • Retention schedule
        • Large Service-Based Network with Small Budget
          • Backup plan
          • Retention schedule
        • Large Service-Based Networks with Large Budget
          • Backup plan
          • Retention schedule
      • Backing Up System Files
        • Which Files to Back Up?
        • Building an Automatic Backup System
      • Software for Backups
        • Simple Local Copies
        • Simple Archives
        • Specialized Backup Programs
        • Network Backup Systems
        • Encrypting Your Backups
      • Summary
    • 19. Defending Accounts
      • Dangerous Accounts
        • Accounts Without Passwords
        • Default Accounts
          • The superuser account
          • Other accounts
        • Accounts That Run a Single Command
        • Open Accounts
          • Restricted shells
          • How to set up a restricted account with rsh
          • Potential problems with restricted shells
        • Restricted Filesystem with the chroot( ) Jail
          • Setting up the chroot( ) environment
          • Limiting network servers
          • Limiting users
          • Checking new software
        • Group Accounts
      • Monitoring File Format
      • Restricting Logins
      • Managing Dormant Accounts
        • Disabling an Account by Changing the Accounts Password
        • Changing the Accounts Login Shell
        • Finding Dormant Accounts
      • Protecting the root Account
        • Secure Terminals
        • The wheel Group
        • The sudo Program
        • Trusted Path and Trusted Computing Base
          • Trusted path
          • Trusted computing base
      • One-Time Passwords
        • Integrating One-Time Passwords with Unix
        • Token Cards
        • Codebooks
      • Administrative Techniques for Conventional Passwords
        • Assigning Passwords to Users
        • Constraining Passwords
        • Password Generators
        • Shadow Password Files
        • Password Aging and Expiration
        • Cracking Your Own Passwords
          • Joetest: a simple password cracker
          • The dilemma of password crackers
        • Algorithm and Library Changes
        • Account Names Revisited: Using Aliases for Increased Security
      • Intrusion Detection Systems
      • Summary
    • 20. Integrity Management
      • The Need for Integrity
      • Protecting Integrity
        • Immutable and Append-Only Files
          • The chflags command
          • Kernel security level
        • Read-Only Filesystems
      • Detecting Changes After the Fact
        • The Achilles Heel of Integrity Management Systems
        • Comparison Copies
          • Local copies
          • Remote copies
          • rdist
        • Checklists and Metadata
          • Simple listing
          • Ancestor directories
        • Checksums and Signatures
      • Integrity-Checking Tools
        • BSDs mtree and Periodic Security Scans
        • Packaging Tools
          • Integrity checking with RPM under Linux
          • Integrity checking with the BSD pkg_info command
        • Tripwire
          • Building Tripwire
          • Running Tripwire
      • Summary
    • 21. Auditing, Logging, and Forensics
      • Unix Log File Utilities
        • Essential Log Files
        • Unix syslog
          • The syslog message
          • The syslog.conf configuration file
          • Using syslog in a networked environment
          • Incorporating syslog into your own programs
          • Beware false syslog log entries
        • Rotating Logs with newsyslog
        • Swatch: A Log File Analysis Tool
          • Running Swatch
          • The Swatch configuration file
        • lastlog File
        • utmp and wtmp Files
          • Examining the utmp and wtmp files
          • The su command and the utmp and wtmp files
          • last program
          • Pruning the wtmp file
        • loginlog File
      • Process Accounting: The acct/pacct File
        • Accounting with System V
        • Accounting with BSD and Linux
        • messages Log File
      • Program-Specific Log Files
        • aculog Log File
        • sulog Log File
        • xferlog Log File
        • access_log Log File
        • Logging Network Services
        • Other Logs
      • Designing a Site-Wide Log Policy
        • Where to Log
          • Logging to a printer
          • Logging across the network
          • Logging everything everywhere
      • Handwritten Logs
        • Per-Site Logs
          • Exception and activity reports
          • Informational material
        • Per-Machine Logs
          • Exception and activity reports
          • Informational material
      • Managing Log Files
      • Unix Forensics
        • Shell History
        • Mail
        • cron
        • Network Setup
      • Summary
  • V. Handling Security Incidents
    • 22. Discovering a Break-in
      • Prelude
        • Rule #1: Dont Panic
        • Rule #2: Document
        • Rule #3: Plan Ahead
      • Discovering an Intruder
        • Catching One in the Act
          • Monitoring commands
          • Other tip-offs
        • What to Do When You Catch Somebody
        • Contacting the Intruder
        • Monitoring the Intruder
        • Tracing a Connection
        • How to Contact the System Administrator of a Computer You Dont Know
          • Looking up information by domain
          • Looking up information by IP address
          • Contacting a sites ISP
          • Alternative contact strategies
        • Getting Rid of the Intruder
      • Cleaning Up After the Intruder
        • Analyzing the Log Files
        • Preserving the Evidence
        • Assessing the Damage
          • New accounts
          • Changes in file contents
          • Changes in file and directory protections
          • New SUID and SGID files
          • Changes in .rhosts files
          • Changes to .ssh/authorized_keys files
          • Changes to the /etc/hosts.equiv file
          • Changes to startup files
          • Hidden files and directories
          • Unowned files
          • New network services
        • Never Trust Anything Except Hardcopy
        • Resuming Operation
        • Damage Control
      • Case Studies
        • Rootkit
        • Warez
          • The follow-up
        • faxsurvey
      • Summary
    • 23. Protecting Against Programmed Threats
      • Programmed Threats: Definitions
        • Security Scanners and Other Tools
        • Back Doors and Trap Doors
        • Logic Bombs
        • Trojan Horses
          • Trojan horses in mobile code
          • Terminal-based Trojan horses
          • Avoiding Trojan horses
        • Viruses
        • Worms
        • Bacteria and Rabbits
      • Damage
      • Authors
      • Entry
      • Protecting Yourself
        • Shell Features
          • PATH attacks
          • IFS attacks
          • $HOME attacks
          • Filename attacks
        • Startup File Attacks
          • .login, .profile, /etc/profile
          • .cshrc, .kshrc, .tcshrc
          • .emacs
          • .exrc, .nexrc
          • .forward, .procmailrc
          • Other files
          • Other initializations
        • Abusing Automatic Mechanisms
          • crontab entries
          • inetd.conf
          • /etc/mail/aliases, aliases.dir, aliases.pag, and aliases.db
          • The at program
          • System initialization files
          • Other files
          • Issues with NFS
      • Preventing Attacks
        • File Protections
          • World-writable user files and directories
          • Writable system files and directories
          • Group-writable files
          • World-readable backup devices
        • Shared Libraries
      • Summary
    • 24. Denial of Service Attacks and Solutions
      • Types of Attacks
      • Destructive Attacks
      • Overload Attacks
        • Process and CPU Overload Problems
          • Too many processes
          • Recovering from too many processes
          • No more processes
          • Safely halting the system
          • CPU overload attacks
        • Swap Space Problems
          • Swapping to files
        • Disk Attacks
          • Disk-full attacks
          • quot command
          • inode problems
          • Using partitions to protect your users
          • Using quotas
          • Reserved space
          • Hidden space
          • Tree structure attacks
        • /tmp Problems
        • Soft Process Limits: Preventing Accidental Denial of Service
      • Network Denial of Service Attacks
        • Service Overloading
        • Message Flooding
        • Signal Grounding and Jamming
        • Clogging (SYN Flood Attacks)
        • Ping of Death and Other Malformed Traffic Attacks
      • Summary
    • 25. Computer Crime
      • Your Legal Options After a Break-in
        • Filing a Criminal Complaint
          • Choosing jurisdiction
          • Local jurisdiction
          • Federal jurisdiction
        • Federal Computer Crime Laws
        • Hazards of Criminal Prosecution
        • The Responsibility to Report Crime
      • Criminal Hazards
      • Criminal Subject Matter
        • Access Devices and Copyrighted Software
        • Pornography, Indecency, and Obscenity
          • Amateur Action
          • Communications Decency Act
          • Mandatory blocking
          • Child pornography
        • Copyrighted Works
        • Cryptographic Programs and Export Controls
      • Summary
    • 26. Who Do You Trust?
      • Can You Trust Your Computer?
        • Harrys Compiler
        • Trusting Trust
        • What the Superuser Can and Cannot Do
      • Can You Trust Your Suppliers?
        • Hardware Bugs
        • Viruses on the Distribution Disk
        • Buggy Software
        • Hacker Challenges
        • Security Bugs That Never Get Fixed
        • Network Providers That Network Too Well
      • Can You Trust People?
        • Your Employees?
        • Your System Administrator?
        • Your Vendor?
        • Your Consultants?
        • Response Personnel?
      • Summary
  • VI. Appendixes
    • A. Unix Security Checklist
      • Preface
      • Chapter 1: Introduction: Some Fundamental Questions
      • Chapter 2: Unix History and Lineage
      • Chapter 3: Policies and Guidelines
      • Chapter 4: Users, Passwords, and Authentication
      • Chapter 5: Users, Groups, and the Superuser
      • Chapter 6: Filesystems and Security
      • Chapter 7: Cryptography Basics
      • Chapter 8: Physical Security for Servers
      • Chapter 9: Personnel Security
      • Chapter 10: Modems and Dialup Security
      • Chapter 11: TCP/IP Networks
      • Chapter 12: Securing TCP and UDP Services
      • Chapter 13: Sun RPC
      • Chapter 14: Network-Based Authentication Systems
      • Chapter 15: Network Filesystems
      • Chapter 16: Secure Programming Techniques
      • Chapter 17: Keeping Up to Date
      • Chapter 18: Backups
      • Chapter 19: Defending Accounts
      • Chapter 20: Integrity Management
      • Chapter 21: Auditing, Logging, and Forensics
      • Chapter 22: Discovering a Break-In
      • Chapter 23: Protecting Against Programmed Threats
      • Chapter 24: Denial of Service Attacks and Solutions
      • Chapter 25: Computer Crime
      • Chapter 26: Who Do You Trust?
      • Appendix A: Unix Security Checklist
      • Appendix B: Unix Processes
      • Appendixes C, D, and E: Paper Sources, Electronic Sources, and Organizations
    • B. Unix Processes
      • About Processes
        • Processes and Programs
        • The ps Command
          • Listing processes with Solaris and other Unix systems derived from System V
          • Listing processes with versions of Unix derived from BSD, including Linux
        • Process Properties
          • Process identification numbers (PIDs)
          • Process real and effective UIDs
          • Process priority and niceness
          • Process groups and sessions
        • Creating Processes
      • Signals
        • Unix Signals and the kill Command
        • Killing Multiple Processes at the Same Time
        • Catching Signals
        • Killing Rogue or Questionable Processes
      • Controlling and Examining Processes
        • gdb: Controlling a Process
        • gcore: Dumping Core
        • lsof: Examining a Process
        • /proc: Examining a Process Directly
        • pstree: Viewing the Process Tree
      • Starting Up Unix and Logging In
        • Process #1: /etc/init
        • Logging In
        • Running the Users Shell
    • C. Paper Sources
      • Unix Security References
      • Other Computer References
        • Computer Crime and Law
        • Computer-Related Risks
        • Computer Viruses and Programmed Threats
        • Cryptography Books
        • Cryptography Papers and Other Publications
        • General Computer Security
        • Network Technology and Security
        • Security Products and Services Information
        • Understanding the Computer Security Culture
        • Unix Programming and System Administration
        • Miscellaneous References
        • Security Periodicals
    • D. Electronic Resources
      • Mailing Lists
        • Response Teams and Vendors
        • A Big Problem with Mailing Lists
        • Major Mailing Lists
          • Bugtraq
          • CERT-advisory
          • Computer underground digest
          • Firewalls
          • Firewall-Wizards
          • RISKS
          • SANS Security Alert Consensus
      • Web Sites
        • CIAC
        • CERIAS
        • FIRST
        • NIST CSRC
        • Insecure.org
        • NIH
      • Usenet Groups
      • Software Resources
        • chrootuid
        • COPS (Computer Oracle and Password System)
        • ISS (Internet Security Scanner)
        • Kerberos
        • nmap
        • Nessus
        • OpenSSH
        • OpenSSL
        • portmap
        • portsentry
        • SATAN
        • Snort
        • Swatch
        • TCP Wrappers
        • Tiger
        • trimlog
        • Tripwire
        • wuarchive ftpd
    • E. Organizations
      • Professional Organizations
        • Association for Computing Machinery (ACM)
        • American Society for Industrial Security (ASIS)
        • Computer Security Institute (CSI)
        • Electronic Frontier Foundation (EFF)
        • Electronic Privacy Information Center (EPIC)
        • High Technology Crimes Investigation Association (HTCIA)
        • Information Systems Security Association (ISSA)
        • International Information Systems Security Certification Consortium, Inc.
        • The Internet Society
        • IEEE Computer Society
        • IFIP, Technical Committee 11
        • Systems Administration and Network Security (SANS)
        • USENIX/SAGE
      • U.S. Government Organizations
        • National Institute of Standards and Technology (NIST)
        • National Security Agency (NSA)
      • Emergency Response Organizations
        • Department of Justice (DOJ)
        • Federal Bureau of Investigation (FBI)
        • U.S. Secret Service (USSS)
        • Forum of Incident and Response Security Teams (FIRST)
        • Computer Emergency Response Team Coordination Center (CERT/CC)
  • Index
  • About the Authors
  • Colophon
  • SPECIAL OFFER: Upgrade this ebook with OReilly

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