Building Internet Firewalls. 2nd Edition

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• Building Internet Firewalls, 2nd Edition
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  • Preface
    • Scope of This Book
    • Audience
    • Platforms
    • Products
    • Examples
    • Conventions Used in This Book
    • Comments and Questions
    • Acknowledgments for the Second Edition
    • Acknowledgments for the First Edition
  • I. Network Security
    • 1. Why Internet Firewalls?
      • 1.1. What Are You Trying to Protect?
        • 1.1.1. Your Data
        • 1.1.2. Your Resources
        • 1.1.3. Your Reputation
      • 1.2. What Are You Trying to Protect Against?
        • 1.2.1. Types of Attacks
          • 1.2.1.1. Intrusion
          • 1.2.1.2. Denial of service
          • 1.2.1.3. Information theft
        • 1.2.2. Types of Attackers
          • 1.2.2.1. Joyriders
          • 1.2.2.2. Vandals
          • 1.2.2.3. Scorekeepers
          • 1.2.2.4. Spies (industrial and otherwise)
        • 1.2.3. Stupidity and Accidents
        • 1.2.4. Theoretical Attacks
      • 1.3. Who Do You Trust?
      • 1.4. How Can You Protect Your Site?
        • 1.4.1. No Security
        • 1.4.2. Security Through Obscurity
        • 1.4.3. Host Security
        • 1.4.4. Network Security
        • 1.4.5. No Security Model Can Do It All
      • 1.5. What Is an Internet Firewall?
        • 1.5.1. What Can a Firewall Do?
          • 1.5.1.1. A firewall is a focus for security decisions
          • 1.5.1.2. A firewall can enforce a security policy
          • 1.5.1.3. A firewall can log Internet activity efficiently
          • 1.5.1.4. A firewall limits your exposure
        • 1.5.2. What Cant a Firewall Do?
          • 1.5.2.1. A firewall can't protect you against malicious insiders
          • 1.5.2.2. A firewall can't protect you against connections that don't go through it
          • 1.5.2.3. A firewall can't protect against completely new threats
          • 1.5.2.4. A firewall can't fully protect against viruses
          • 1.5.2.5. A firewall can't set itself up correctly
        • 1.5.3. What's Wrong with Firewalls?
          • 1.5.3.1. Firewalls interfere with the Internet
          • 1.5.3.2. Firewalls don't deal with the real problem
      • 1.6. Religious Arguments
        • 1.6.1. Buying Versus Building
        • 1.6.2. Unix Versus Windows NT
        • 1.6.3. That's Not a Firewall!
    • 2. Internet Services
      • 2.1. Secure Services and Safe Services
      • 2.2. The World Wide Web
        • 2.2.1. Web Client Security Issues
        • 2.2.2. Web Server Security Issues
      • 2.3. Electronic Mail and News
        • 2.3.1. Electronic Mail
        • 2.3.2. Usenet News
      • 2.4. File Transfer, File Sharing, and Printing
        • 2.4.1. File Transfer
        • 2.4.2. File Sharing
        • 2.4.3. Printing Systems
      • 2.5. Remote Access
        • 2.5.1. Remote Terminal Access and Command Execution
        • 2.5.2. Remote Graphic Interfaces for Microsoft Operating Systems
        • 2.5.3. Network Window Systems
      • 2.6. Real-Time Conferencing Services
      • 2.7. Naming and Directory Services
      • 2.8. Authentication and Auditing Services
      • 2.9. Administrative Services
        • 2.9.1. System Management
        • 2.9.2. Routing
        • 2.9.3. Network Diagnostics
        • 2.9.4. Time Service
      • 2.10. Databases
      • 2.11. Games
    • 3. Security Strategies
      • 3.1. Least Privilege
      • 3.2. Defense in Depth
      • 3.3. Choke Point
      • 3.4. Weakest Link
      • 3.5. Fail-Safe Stance
        • 3.5.1. Default Deny Stance: That Which Is Not Expressly Permitted Is Prohibited
        • 3.5.2. Default Permit Stance: That Which Is Not Expressly Prohibited Is Permitted
      • 3.6. Universal Participation
      • 3.7. Diversity of Defense
        • 3.7.1. Inherent Weaknesses
        • 3.7.2. Common Configuration
        • 3.7.3. Common Heritage
        • 3.7.4. Skin-Deep Differences
        • 3.7.5. Conclusion
      • 3.8. Simplicity
      • 3.9. Security Through Obscurity
  • II. Building Firewalls
    • 4. Packets and Protocols
      • 4.1. What Does a Packet Look Like?
        • 4.1.1. TCP/IP/Ethernet Example
          • 4.1.1.1. Ethernet layer
          • 4.1.1.2. IP layer
          • 4.1.1.3. TCP layer
      • 4.2. IP
        • 4.2.1. IP Multicast and Broadcast
        • 4.2.2. IP Options
        • 4.2.3. IP Fragmentation
      • 4.3. Protocols Above IP
        • 4.3.1. TCP
          • 4.3.1.1. TCP options
          • 4.3.1.2. TCP sequence numbers
        • 4.3.2. UDP
        • 4.3.3. ICMP
        • 4.3.4. IP over IP and GRE
      • 4.4. Protocols Below IP
      • 4.5. Application Layer Protocols
      • 4.6. IP Version 6
      • 4.7. Non-IP Protocols
      • 4.8. Attacks Based on Low-Level Protocol Details
        • 4.8.1. Port Scanning
        • 4.8.2. Implementation Weaknesses
        • 4.8.3. IP Spoofing
          • 4.8.3.1. The attacker can intercept the reply
          • 4.8.3.2. The attacker doesn't need to see the reply
          • 4.8.3.3. The attacker doesn't want the reply
        • 4.8.4. Packet Interception
    • 5. Firewall Technologies
      • 5.1. Some Firewall Definitions
      • 5.2. Packet Filtering
        • 5.2.1. Advantages of Packet Filtering
          • 5.2.1.1. One screening router can help protect an entire network
          • 5.2.1.2. Simple packet filtering is extremely efficient
          • 5.2.1.3. Packet filtering is widely available
        • 5.2.2. Disadvantages of Packet Filtering
          • 5.2.2.1. Current filtering tools are not perfect
          • 5.2.2.2. Packet filtering reduces router performance
          • 5.2.2.3. Some policies can't readily be enforced by normal packet filtering routers
      • 5.3. Proxy Services
        • 5.3.1. Advantages of Proxying
          • 5.3.1.1. Proxy services can be good at logging
          • 5.3.1.2. Proxy services can provide caching
          • 5.3.1.3. Proxy services can do intelligent filtering
          • 5.3.1.4. Proxy systems can perform user-level authentication
          • 5.3.1.5. Proxy systems automatically provide protection for weak or faulty IP implementations
        • 5.3.2. Disadvantages of Proxying
          • 5.3.2.1. Proxy services lag behind nonproxied services
          • 5.3.2.2. Proxy services may require different servers for each service
          • 5.3.2.3. Proxy services usually require modifications to clients, applications, or procedures
      • 5.4. Network Address Translation
        • 5.4.1. Advantages of Network Address Translation
          • 5.4.1.1. Network address translation helps to enforce the firewall's control over outbound connections
          • 5.4.1.2. Network address translation can help restrict incoming traffic
          • 5.4.1.3. Network address translation helps to conceal the internal network's configuration
        • 5.4.2. Disadvantages of Network Address Translation
          • 5.4.2.1. Dynamic allocation requires state information that is not always available
          • 5.4.2.2. Embedded IP addresses are a problem for network address translation
          • 5.4.2.3. Network address translation interferes with some encryption and authentication systems
          • 5.4.2.4. Dynamic allocation of addresses interferes with logging
          • 5.4.2.5. Dynamic allocation of ports may interfere with packet filtering
      • 5.5. Virtual Private Networks
        • 5.5.1. Where Do You Encrypt?
        • 5.5.2. Key Distribution and Certificates
        • 5.5.3. Advantages of Virtual Private Networks
          • 5.5.3.1. Virtual private networks provide overall encryption
          • 5.5.3.2. Virtual private networks allow you to remotely use protocols that are difficult to secure any other way
        • 5.5.4. Disadvantages of Virtual Private Networks
          • 5.5.4.1. Virtual private networks involve dangerous network connections
          • 5.5.4.2. Virtual private networks extend the network you must protect
    • 6. Firewall Architectures
      • 6.1. Single-Box Architectures
        • 6.1.1. Screening Router
          • 6.1.1.1. Appropriate uses
        • 6.1.2. Dual-Homed Host
          • 6.1.2.1. Appropriate uses
        • 6.1.3. Multiple-Purpose Boxes
          • 6.1.3.1. Appropriate uses
      • 6.2. Screened Host Architectures
        • 6.2.1. Appropriate Uses
      • 6.3. Screened Subnet Architectures
        • 6.3.1. Perimeter Network
        • 6.3.2. Bastion Host
        • 6.3.3. Interior Router
        • 6.3.4. Exterior Router
        • 6.3.5. Appropriate Uses
      • 6.4. Architectures with Multiple Screened Subnets
        • 6.4.1. Split-Screened Subnet
          • 6.4.1.1. Appropriate uses
        • 6.4.2. Independent Screened Subnets
          • 6.4.2.1. Appropriate uses
      • 6.5. Variations on Firewall Architectures
        • 6.5.1. It's OK to Use Multiple Bastion Hosts
        • 6.5.2. It's OK to Merge the Interior Router and the Exterior Router
        • 6.5.3. It's OK to Merge the Bastion Host and the Exterior Router
        • 6.5.4. It's Dangerous to Merge the Bastion Host and the Interior Router
        • 6.5.5. It's Dangerous to Use Multiple Interior Routers
        • 6.5.6. It's OK to Use Multiple Exterior Routers
        • 6.5.7. It's Dangerous to Use Both Screened Subnets and Screened Hosts
      • 6.6. Terminal Servers and Modem Pools
      • 6.7. Internal Firewalls
        • 6.7.1. Laboratory Networks
        • 6.7.2. Insecure Networks
        • 6.7.3. Extra-Secure Networks
        • 6.7.4. Joint Venture Firewalls
        • 6.7.5. A Shared Perimeter Network Allows an "Arms-Length"Relationship
        • 6.7.6. An Internal Firewall May or May Not Need Bastion Hosts
    • 7. Firewall Design
      • 7.1. Define Your Needs
        • 7.1.1. What Will the Firewall Actually Do?
          • 7.1.1.1. What services do you need to offer?
          • 7.1.1.2. How secure do you need to be?
          • 7.1.1.3. How much usage will there be?
          • 7.1.1.4. How much reliability do you need?
        • 7.1.2. What Are Your Constraints?
          • 7.1.2.1. What budget do you have available?
          • 7.1.2.2. What personnel do you have available?
          • 7.1.2.3. What is your environment like?
      • 7.2. Evaluate the Available Products
        • 7.2.1. Scalability
        • 7.2.2. Reliability and Redundancy
        • 7.2.3. Auditability
        • 7.2.4. Price
        • 7.2.5. Management and Configuration
        • 7.2.6. Adaptability
        • 7.2.7. Appropriateness
      • 7.3. Put Everything Together
        • 7.3.1. Where will logs go, and how?
          • 7.3.1.1. How will you back up the system?
          • 7.3.1.2. What support services does the system require?
          • 7.3.1.3. How will you access the machines?
          • 7.3.1.4. Where will routine reports go, and how?
          • 7.3.1.5. Where will alarms go, and how?
    • 8. Packet Filtering
      • 8.1. What Can You Do with Packet Filtering?
        • 8.1.1. Basic Packet Filtering
        • 8.1.2. Stateful or Dynamic Packet Filtering
        • 8.1.3. Protocol Checking
      • 8.2. Configuring a Packet Filtering Router
        • 8.2.1. Protocols Are Usually Bidirectional
        • 8.2.2. Be Careful of "Inbound" Versus "Outbound" Semantics
        • 8.2.3. Default Permit Versus Default Deny
      • 8.3. What Does the Router Do with Packets?
        • 8.3.1. Logging Actions
        • 8.3.2. Returning Error Codes
        • 8.3.3. Making Changes
      • 8.4. Packet Filtering Tips and Tricks
        • 8.4.1. Edit Your Filtering Rules Offline
        • 8.4.2. Reload Rule Sets from Scratch Each Time
        • 8.4.3. Replace Packet Filters Atomically
        • 8.4.4. Always Use IP Addresses, Never Hostnames
        • 8.4.5. Password Protect Your Packet Filters
        • 8.4.6. If Possible, Use Named Access Lists
      • 8.5. Conventions for Packet Filtering Rules
      • 8.6. Filtering by Address
        • 8.6.1. Risks of Filtering by Source Address
      • 8.7. Filtering by Service
        • 8.7.1. Outbound Telnet Service
        • 8.7.2. Inbound Telnet Service
        • 8.7.3. Telnet Summary
        • 8.7.4. Risks of Filtering by Source Port
      • 8.8. Choosing a Packet Filtering Router
        • 8.8.1. It Should Have Good Enough Packet Filtering Performance for Your Needs
        • 8.8.2. It Can Be a Single-Purpose Router or a General-Purpose Computer
        • 8.8.3. It Should Allow Simple Specification of Rules
        • 8.8.4. It Should Allow Rules Based on Any Header or Meta-Packet Criteria
        • 8.8.5. It Should Apply Rules in the Order Specified
          • 8.8.5.1. If the rules are applied in the order ABC
          • 8.8.5.2. If the rules are applied in the order BAC
          • 8.8.5.3. Rule B is actually not necessary
          • 8.8.5.4. Packet filtering rules are tricky
        • 8.8.6. It Should Apply Rules Separately to Incoming and Outgoing Packets, on a Per-Interface Basis
        • 8.8.7. It Should Be Able to Log Accepted and Dropped Packets
        • 8.8.8. It Should Have Good Testing and Validation Capabilities
      • 8.9. Packet Filtering Implementations for General-Purpose Computers
        • 8.9.1. Linux ipchains and Masquerading
          • 8.9.1.1. ipchains
          • 8.9.1.2. Testing ipchains rules
          • 8.9.1.3. Masquerading
          • 8.9.1.4. How masquerading works
          • 8.9.1.5. Available specialized masquerading modules
          • 8.9.1.6. Using ipchains (including masquerading)
        • 8.9.2. ipfilter
        • 8.9.3. Comparing ipfilter and ipchains
        • 8.9.4. Linux netfilter
        • 8.9.5. Windows NT Packet Filtering
      • 8.10. Where to Do Packet Filtering
      • 8.11. What Rules Should You Use?
      • 8.12. Putting It All Together
    • 9. Proxy Systems
      • 9.1. Why Proxying?
      • 9.2. How Proxying Works
        • 9.2.1. Using Proxy-Aware Application Software for Proxying
        • 9.2.2. Using Proxy-Aware Operating System Software
        • 9.2.3. Using Proxy-Aware User Procedures for Proxying
        • 9.2.4. Using a Proxy-Aware Router
      • 9.3. Proxy Server Terminology
        • 9.3.1. Application-Level Versus Circuit-Level Proxies
        • 9.3.2. Generic Versus Dedicated Proxies
        • 9.3.3. Intelligent Proxy Servers
      • 9.4. Proxying Without a Proxy Server
      • 9.5. Using SOCKS for Proxying
        • 9.5.1. Versions of SOCKS
        • 9.5.2. SOCKS Features
        • 9.5.3. SOCKS Components
        • 9.5.4. Converting Clients to Use SOCKS
      • 9.6. Using the TIS Internet Firewall Toolkit for Proxying
        • 9.6.1. FTP Proxying with TIS FWTK
        • 9.6.2. Telnet and rlogin Proxying with TIS FWTK
        • 9.6.3. Generic Proxying with TIS FWTK
        • 9.6.4. Other TIS FWTK Proxies
      • 9.7. Using Microsoft Proxy Server
        • 9.7.1. Proxy Server and SOCKS
        • 9.7.2. Proxy Server and WinSock
      • 9.8. What If You Can't Proxy?
        • 9.8.1. No Proxy Server Is Available
        • 9.8.2. Proxying Won't Secure the Service
        • 9.8.3. Can't Modify Client or Procedures
    • 10. Bastion Hosts
      • 10.1. General Principles
      • 10.2. Special Kinds of Bastion Hosts
        • 10.2.1. Nonrouting Dual-Homed Hosts
        • 10.2.2. Victim Machines
        • 10.2.3. Internal Bastion Hosts
        • 10.2.4. External Service Hosts
        • 10.2.5. One-Box Firewalls
      • 10.3. Choosing a Machine
        • 10.3.1. What Operating System?
        • 10.3.2. How Fast a Machine?
        • 10.3.3. What Hardware Configuration?
      • 10.4. Choosing a Physical Location
      • 10.5. Locating Bastion Hosts on the Network
      • 10.6. Selecting Services Provided by a Bastion Host
        • 10.6.1. Multiple Services or Multiple Hosts?
      • 10.7. Disabling User Accounts on Bastion Hosts
      • 10.8. Building a Bastion Host
      • 10.9. Securing the Machine
        • 10.9.1. Start with a Minimal Clean Operating System Installation
        • 10.9.2. Fix All Known System Bugs
        • 10.9.3. Use a Checklist
        • 10.9.4. Safeguard the System Logs
          • 10.9.4.1. System logs for convenience
          • 10.9.4.2. System logs for catastrophes
          • 10.9.4.3. Logging and time
          • 10.9.4.4. Choosing what to log
      • 10.10. Disabling Nonrequired Services
        • 10.10.1. How to Disable Services
          • 10.10.1.1. Next steps after disabling services
        • 10.10.2. Running Services on Specific Networks
        • 10.10.3. Turning Off Routing
        • 10.10.4. Controlling Inbound Traffic
        • 10.10.5. Installing and Modifying Services
        • 10.10.6. Reconfiguring for Production
          • 10.10.6.1. Finalize the operating system configuration
          • 10.10.6.2. Mount filesystems as read-only
        • 10.10.7. Running a Security Audit
          • 10.10.7.1. Auditing packages
          • 10.10.7.2. Use cryptographic checksums for auditing
        • 10.10.8. Connecting the Machine
      • 10.11. Operating the Bastion Host
        • 10.11.1. Learn What the Normal Usage Profile Is
        • 10.11.2. Consider Using Software to Automate Monitoring
      • 10.12. Protecting the Machine and Backups
        • 10.12.1. Watch Reboots Carefully
        • 10.12.2. Do Secure Backups
        • 10.12.3. Other Objects to Secure
    • 11. Unix and Linux Bastion Hosts
      • 11.1. Which Version of Unix?
      • 11.2. Securing Unix
        • 11.2.1. Setting Up System Logs on Unix
          • 11.2.1.1. syslog Linux example
          • 11.2.1.2. System logs for catastrophe
      • 11.3. Disabling Nonrequired Services
        • 11.3.1. How Are Services Managed Under Unix?
          • 11.3.1.1. Services started by /etc/rc files or directories
          • 11.3.1.2. Services started by inetd
        • 11.3.2. Disabling Services Under Unix
        • 11.3.3. Which Services Should You Leave Enabled?
        • 11.3.4. Specific Unix Services to Disable
          • 11.3.4.1. NFS and related services
          • 11.3.4.2. Other RPC services
          • 11.3.4.3. Booting services
          • 11.3.4.4. BSD "r" command services
          • 11.3.4.5. routed
          • 11.3.4.6. fingerd
          • 11.3.4.7. ftpd
          • 11.3.4.8. Other services
        • 11.3.5. Running Services on Specific Networks
        • 11.3.6. Turning Off Routing
      • 11.4. Installing and Modifying Services
        • 11.4.1. Using the TCP Wrapper Package to Protect Services
          • 11.4.1.1. TCP Wrapper example
          • 11.4.1.2. Using netacl to protect services
        • 11.4.2. Evaluating and Configuring Unix Services
      • 11.5. Reconfiguring for Production
        • 11.5.1. Reconfigure and Rebuild the Kernel
        • 11.5.2. Remove Nonessential Programs
        • 11.5.3. Mount Filesystems as Read-Only
      • 11.6. Running a Security Audit
    • 12. Windows NT and Windows 2000 Bastion Hosts
      • 12.1. Approaches to Building Windows NT Bastion Hosts
      • 12.2. Which Version of Windows NT?
      • 12.3. Securing Windows NT
        • 12.3.1. Setting Up System Logs Under Windows NT
      • 12.4. Disabling Nonrequired Services
        • 12.4.1. How Are Services Managed Under Windows NT?
          • 12.4.1.1. Registry keys
          • 12.4.1.2. Other ways to start programs under Windows NT
        • 12.4.2. How to Disable Services Under Windows NT
        • 12.4.3. Next Steps After Disabling Services
        • 12.4.4. Which Services Should You Leave Enabled?
        • 12.4.5. Specific Windows NT Services to Disable
          • 12.4.5.1. The Services control panel
        • 12.4.6. Turning Off Routing
      • 12.5. Installing and Modifying Services
  • III. Internet Services
    • 13. Internet Services and Firewalls
      • 13.1. Attacks Against Internet Services
        • 13.1.1. Command-Channel Attacks
        • 13.1.2. Data-Driven Attacks
        • 13.1.3. Third-Party Attacks
        • 13.1.4. False Authentication of Clients
        • 13.1.5. Hijacking
        • 13.1.6. Packet Sniffing
        • 13.1.7. Data Injection and Modification
        • 13.1.8. Replay
        • 13.1.9. Denial of Service
        • 13.1.10. Protecting Services
      • 13.2. Evaluating the Risks of a Service
        • 13.2.1. What Operations Does the Protocol Allow?
          • 13.2.1.1. What is it designed to do?
          • 13.2.1.2. Is the level of authentication and authorization it uses appropriate for doing that?
          • 13.2.1.3. Does it have any other commands in it?
        • 13.2.2. What Data Does the Protocol Transfer?
        • 13.2.3. How Well Is the Protocol Implemented?
          • 13.2.3.1. Does it have any other commands in it?
        • 13.2.4. What Else Can Come in If I Allow This Service?
      • 13.3. Analyzing Other Protocols
      • 13.4. What Makes a Good Firewalled Service?
        • 13.4.1. TCP Versus Other Protocols
        • 13.4.2. One Connection per Session
        • 13.4.3. One Session per Connection
        • 13.4.4. Assigned Ports
        • 13.4.5. Protocol Security
      • 13.5. Choosing Security-Critical Programs
        • 13.5.1. My Product Is Secure Because . . .
          • 13.5.1.1. It contains no publicly available code, so it's secret
          • 13.5.1.2. It contains publicly available code, so it's been well reviewed
          • 13.5.1.3. It is built entirely from scratch, so it didn't inherit any bugs from any other products
          • 13.5.1.4. It is built on an old, well-tested code base
          • 13.5.1.5. It doesn't run as root/Administrator/LocalSystem
          • 13.5.1.6. It doesn't run under Unix, or it doesn't run on a Microsoft operating system
          • 13.5.1.7. There are no known attacks against it
          • 13.5.1.8. It uses public key cryptography (or some other secure-sounding technology)
        • 13.5.2. Their Product Is Insecure Because . . .
          • 13.5.2.1. It's been mentioned in a CERT-CC advisory or on a web site listing vulnerabilities
          • 13.5.2.2. It's publicly available
          • 13.5.2.3. It's been successfully attacked
        • 13.5.3. Real Indicators of Security
          • 13.5.3.1. Security was one of the design criteria
          • 13.5.3.2. The supplier can discuss how major security problems were avoided
          • 13.5.3.3. It is possible for you to review the code
          • 13.5.3.4. Somebody you know and trust actually has reviewed the code
          • 13.5.3.5. There is a security notification and update procedure
          • 13.5.3.6. The server implements a recent (but accepted) version of the protocol
          • 13.5.3.7. The program uses standard error-logging mechanisms
          • 13.5.3.8. There is a secure software distribution mechanism
      • 13.6. Controlling Unsafe Configurations
    • 14. Intermediary Protocols
      • 14.1. Remote Procedure Call (RPC)
        • 14.1.1. Sun RPC Authentication
        • 14.1.2. Microsoft RPC Authentication
        • 14.1.3. Packet Filtering Characteristics of RPC
        • 14.1.4. Proxying Characteristics of RPC
        • 14.1.5. Network Address Translation Characteristics of RPC
        • 14.1.6. Summary of Recommendations for RPC
      • 14.2. Distributed Component Object Model (DCOM)
      • 14.3. NetBIOS over TCP/IP (NetBT)
        • 14.3.1. Packet Filtering Characteristics of NetBT
        • 14.3.2. Proxying Characteristics of NetBT
        • 14.3.3. Network Address Translation Characteristics of NetBT
        • 14.3.4. Summary of Recommendations for NetBT
      • 14.4. Common Internet File System (CIFS) and Server Message Block (SMB)
        • 14.4.1. Authentication and SMB
          • 14.4.1.1. Share-level authentication
          • 14.4.1.2. User-level authentication
        • 14.4.2. Packet Filtering Characteristics of SMB
        • 14.4.3. Proxying Characteristics of SMB
        • 14.4.4. Network Address Translation Characteristics of SMB
        • 14.4.5. Summary of Recommendations for SMB
      • 14.5. Common Object Request Broker Architecture (CORBA) and Internet Inter-Orb Protocol (IIOP)
        • 14.5.1. Packet Filtering Characteristics of CORBA and IIOP
        • 14.5.2. Proxying Characteristics of CORBA and IIOP
        • 14.5.3. Network Address Translation Characteristics of CORBA and IIOP
        • 14.5.4. Summary of Recommendations for CORBA and IIOP
      • 14.6. ToolTalk
        • 14.6.1. Summary of Recommendations for ToolTalk
      • 14.7. Transport Layer Security (TLS) and Secure Socket Layer (SSL)
        • 14.7.1. The TLS and SSL Protocols
        • 14.7.2. Cryptography in TLS and SSL
        • 14.7.3. Use of TLS and SSL by Other Protocols
        • 14.7.4. Packet Filtering Characteristics of TLS and SSL
        • 14.7.5. Proxying Characteristics of TLS and SSL
        • 14.7.6. Network Address Translation Characteristics of TLS and SSL
        • 14.7.7. Summary of Recommendations for TLS and SSL
      • 14.8. The Generic Security Services API (GSSAPI)
      • 14.9. IPsec
        • 14.9.1. Packet Filtering Characteristics of IPsec
        • 14.9.2. Proxying Characteristics of IPsec
        • 14.9.3. Network Address Translation Characteristics of IPsec
        • 14.9.4. Summary of Recommendations for IPsec
      • 14.10. Remote Access Service (RAS)
      • 14.11. Point-to-Point Tunneling Protocol (PPTP)
        • 14.11.1. Design Weaknesses in PPTP
        • 14.11.2. Implementation Weaknesses in PPTP
        • 14.11.3. Packet Filtering Characteristics of PPTP
        • 14.11.4. Proxying Characteristics of PPTP
        • 14.11.5. Network Address Translation Characteristics of PPTP
        • 14.11.6. Summary of Recommendations for PPTP
      • 14.12. Layer 2 Transport Protocol (L2TP)
        • 14.12.1. Packet Filtering Characteristics of L2TP
        • 14.12.2. Proxying Characteristics of L2TP
        • 14.12.3. Network Address Translation Characteristics of L2TP
        • 14.12.4. Summary of Recommendations for L2TP
    • 15. The World Wide Web
      • 15.1. HTTP Server Security
        • 15.1.1. HTTP Extensions
          • 15.1.1.1. Tricking extensions
          • 15.1.1.2. Running unexpected external programs
      • 15.2. HTTP Client Security
        • 15.2.1. Inadvertent Release of Information
          • 15.2.1.1. Cookies
        • 15.2.2. External Viewers
        • 15.2.3. Extension Systems
        • 15.2.4. What Can You Do?
        • 15.2.5. Internet Explorer and Security Zones
      • 15.3. HTTP
        • 15.3.1. HTTP Tunneling
        • 15.3.2. Special HTTP Servers
        • 15.3.3. Packet Filtering Characteristics of HTTP
        • 15.3.4. Proxying Characteristics of HTTP
        • 15.3.5. Network Address Translation Characteristics of HTTP
        • 15.3.6. Securing HTTP
          • 15.3.6.1. Packet filtering characteristics of HTTPS and Secure HTTP
          • 15.3.6.2. Proxying characteristics of HTTPS and Secure HTTP
          • 15.3.6.3. Network address translation characteristics of HTTPS and Secure HTTP
        • 15.3.7. Summary of Recommendations for HTTP
      • 15.4. Mobile Code and Web-Related Languages
        • 15.4.1. JavaScript
        • 15.4.2. VBScript
        • 15.4.3. Java
        • 15.4.4. ActiveX
      • 15.5. Cache Communication Protocols
        • 15.5.1. Internet Cache Protocol (ICP)
          • 15.5.1.1. Packet filtering characteristics of ICP
          • 15.5.1.2. Proxying characteristics of ICP
          • 15.5.1.3. Network address translation characteristics of ICP
        • 15.5.2. Cache Array Routing Protocol (CARP)
        • 15.5.3. Web Cache Coordination Protocol (WCCP)
          • 15.5.3.1. Packet filtering characteristics of WCCP
          • 15.5.3.2. Proxying characteristics of WCCP
          • 15.5.3.3. Network address translation characteristics of WCCP
        • 15.5.4. Summary of Recommendations for Cache Communication Protocols
      • 15.6. Push Technologies
        • 15.6.1. Summary of Recommendations for Push Technologies
      • 15.7. RealAudio and RealVideo
        • 15.7.1. Risks of RealServer
        • 15.7.2. Risks of RealAudio and RealVideo Clients
        • 15.7.3. Packet Filtering Characteristics of RealAudio and RealVideo
        • 15.7.4. Proxying Characteristics of RealAudio and RealVideo
        • 15.7.5. Network Address Translation Characteristics of RealAudio and RealVideo
        • 15.7.6. Summary Recommendations for RealAudio and RealVideo
      • 15.8. Gopher and WAIS
        • 15.8.1. Packet Filtering Characteristics of Gopher and WAIS
        • 15.8.2. Proxying Characteristics of Gopher and WAIS
        • 15.8.3. Network Address Translation Characteristics of Gopher and WAIS
        • 15.8.4. Summary of Recommendations for Gopher and WAIS
    • 16. Electronic Mail and News
      • 16.1. Electronic Mail
        • 16.1.1. Keeping Mail Secret
        • 16.1.2. Undesirable Mail
          • 16.1.2.1. Junk mail
          • 16.1.2.2. Viruses and other hostilities
        • 16.1.3. Multimedia Internet Mail Extensions (MIME)
        • 16.1.4. S/MIME and OpenPGP
      • 16.2. Simple Mail Transfer Protocol (SMTP)
        • 16.2.1. Extended SMTP (ESMTP)
        • 16.2.2. TLS/SSL, SSMTP, and STARTTLS
        • 16.2.3. Packet Filtering Characteristics of SMTP
        • 16.2.4. Proxying Characteristics of SMTP
        • 16.2.5. Network Address Translation Characteristics of SMTP
        • 16.2.6. Configuring SMTP to Work with a Firewall
        • 16.2.7. Sendmail
        • 16.2.8. Other Freely Available SMTP Servers for Unix
          • 16.2.8.1. smail
          • 16.2.8.2. Postfix
          • 16.2.8.3. Qmail
        • 16.2.9. Commercial SMTP Servers for Unix
        • 16.2.10. Improving SMTP Security with smap and smapd
        • 16.2.11. biff
        • 16.2.12. SMTP Support in Non-SMTP Mail Systems
        • 16.2.13. SMTP Servers for Windows NT
        • 16.2.14. Summary of Recommendations for SMTP
      • 16.3. Other Mail Transfer Protocols
      • 16.4. Microsoft Exchange
        • 16.4.1. Summary of Recommendations for Microsoft Exchange
      • 16.5. Lotus Notes and Domino
        • 16.5.1. Packet Filtering Characteristics of Lotus Notes
        • 16.5.2. Proxying Characteristics of Lotus Notes
        • 16.5.3. Network Address Translation Characteristics of Lotus Notes
        • 16.5.4. Summary of Recommendations for Lotus Notes
      • 16.6. Post Office Protocol (POP)
        • 16.6.1. Packet Filtering Characteristics of POP
        • 16.6.2. Proxying Characteristics of POP
        • 16.6.3. Network Address Translation Characteristics of POP
        • 16.6.4. Summary of Recommendations for POP
      • 16.7. Internet Message Access Protocol (IMAP)
        • 16.7.1. Packet Filtering Characteristics of IMAP
        • 16.7.2. Proxying Characteristics of IMAP
        • 16.7.3. Network Address Translation Characteristics of IMAP
        • 16.7.4. Summary of Recommendations for IMAP
      • 16.8. Microsoft Messaging API (MAPI)
      • 16.9. Network News Transfer Protocol (NNTP)
        • 16.9.1. Packet Filtering Characteristics of NNTP
        • 16.9.2. Proxying Characteristics of NNTP
        • 16.9.3. Network Address Translation Characteristics of NNTP
        • 16.9.4. Summary of Recommendations for NNTP
    • 17. File Transfer, File Sharing, and Printing
      • 17.1. File Transfer Protocol (FTP)
        • 17.1.1. Packet Filtering Characteristics of FTP
        • 17.1.2. Proxying Characteristics of FTP
        • 17.1.3. Network Address Translation Characteristics of FTP
        • 17.1.4. Providing Anonymous FTP Service
          • 17.1.4.1. Limiting access to information
          • 17.1.4.2. Preventing people from using your server to distribute their data
            • 17.1.4.2.1. Making your incoming directory write-only
            • 17.1.4.2.2. Making anonymous read and anonymous write exclusive
            • 17.1.4.2.3. Disabling the creation of directories and certain files
            • 17.1.4.2.4. Uploading by prearrangement
            • 17.1.4.2.5. Removing the files
          • 17.1.4.3. Preventing people from using your server to attack other machines
          • 17.1.4.4. Using the wuarchive FTP daemon
        • 17.1.5. Summary of Recommendations for FTP
      • 17.2. Trivial File Transfer Protocol (TFTP)
        • 17.2.1. Packet Filtering Characteristics of TFTP
        • 17.2.2. Proxying Characteristics of TFTP
        • 17.2.3. Network Address Translation Characteristics of TFTP
        • 17.2.4. Summary of Recommendations for TFTP
      • 17.3. Network File System (NFS)
        • 17.3.1. NFS Authentication
        • 17.3.2. NFS and root
        • 17.3.3. NFS Client Vulnerabilities
        • 17.3.4. File Locking with NFS
        • 17.3.5. Automounting
        • 17.3.6. Packet Filtering Characteristics of NFS
        • 17.3.7. Proxying Characteristics of NFS
        • 17.3.8. Network Address Translation Characteristics of NFS
      • 17.4. File Sharing for Microsoft Networks
        • 17.4.1. Samba
        • 17.4.2. Distributed File System (Dfs)
        • 17.4.3. Packet Filtering, Proxying, and Network Address Translation Characteristics of Microsoft File Sharing
      • 17.5. Summary of Recommendations for File Sharing
      • 17.6. Printing Protocols
        • 17.6.1. lpr and lp
          • 17.6.1.1. LPRng
          • 17.6.1.2. Packet filtering characteristics of lpr
          • 17.6.1.3. Proxying characteristics of lpr
          • 17.6.1.4. Network address translation characteristics of lpr
          • 17.6.1.5. Packet filtering and proxying characteristics of lp
        • 17.6.2. Windows-based Printing
        • 17.6.3. Other Printing Systems
        • 17.6.4. Summary of Recommendations for Printing Protocols
      • 17.7. Related Protocols
    • 18. Remote Access to Hosts
      • 18.1. Terminal Access (Telnet)
        • 18.1.1. Windows 2000 Telnet
        • 18.1.2. Packet Filtering Characteristics of Telnet
        • 18.1.3. Proxying Characteristics of Telnet
        • 18.1.4. Network Address Translation Characteristics of Telnet
        • 18.1.5. Summary of Recommendations for Telnet
      • 18.2. Remote Command Execution
        • 18.2.1. BSD "r" Commands
          • 18.2.1.1. BSD "r" commands under Windows NT
          • 18.2.1.2. Packet filtering characteristics of the BSD "r" commands
          • 18.2.1.3. Proxying characteristics of the BSD "r" commands
          • 18.2.1.4. Network address translation characteristics of the BSD "r"commands
          • 18.2.1.5. Summary of recommendations for the BSD "r" command
        • 18.2.2. rexec
          • 18.2.2.1. Packet filtering characteristics of rexec
          • 18.2.2.2. Proxying characteristics of rexec
          • 18.2.2.3. Network address translation characteristics of rexec
          • 18.2.2.4. Summary of recommendations for rexec
        • 18.2.3. rex
          • 18.2.3.1. Summary of recommendations for rex
        • 18.2.4. Windows NT Remote Commands
          • 18.2.4.1. Summary of recommendations for remote commands
        • 18.2.5. Secure Shell (SSH)
          • 18.2.5.1. What makes SSH secure?
          • 18.2.5.2. SSH server authentication
          • 18.2.5.3. SSH client authentication
          • 18.2.5.4. Additional SSH options for client control
          • 18.2.5.5. SSH session hijacking protection
          • 18.2.5.6. Port forwarding
          • 18.2.5.7. Remote X11 Window System support
          • 18.2.5.8. Packet filtering characteristics of SSH
          • 18.2.5.9. Proxying characteristics of SSH
          • 18.2.5.10. Network address translation characteristics of SSH
          • 18.2.5.11. Summary of recommendations for SSH
      • 18.3. Remote Graphical Interfaces
        • 18.3.1. X11 Window System
          • 18.3.1.1. Additional servers
          • 18.3.1.2. Packet filtering characteristics of X11
          • 18.3.1.3. Proxying characteristics of X11
          • 18.3.1.4. Network address translation characteristics of X11
          • 18.3.1.5. Summary of recommendations for XII
        • 18.3.2. Remote Graphic Interfaces for Microsoft Operating Systems
        • 18.3.3. Independent Computing Architecture (ICA)
          • 18.3.3.1. Packet filtering characteristics of ICA
          • 18.3.3.2. Proxying characteristics of ICA
          • 18.3.3.3. Network address translation characteristics of ICA
        • 18.3.4. Microsoft Terminal Server and Terminal Services
          • 18.3.4.1. Packet filtering characteristics of RDP
          • 18.3.4.2. Proxying characteristics of RDP
          • 18.3.4.3. Network address translation characteristics of RDP
        • 18.3.5. BO2K
          • 18.3.5.1. Packet filtering characteristics of BO2K
          • 18.3.5.2. Proxying characteristics of BO2K
          • 18.3.5.3. Network address translation characteristics of BO2K
        • 18.3.6. Summary of Recommendations for Windows Remote Access
    • 19. Real-Time Conferencing Services
      • 19.1. Internet Relay Chat (IRC)
        • 19.1.1. Packet Filtering Characteristics of IRC
        • 19.1.2. Proxying Characteristics of IRC
        • 19.1.3. Network Address Translation Characteristics of IRC
        • 19.1.4. Summary of Recommendations for IRC
      • 19.2. ICQ
        • 19.2.1. Packet Filtering Characteristics of ICQ
        • 19.2.2. Proxying Characteristics of ICQ
        • 19.2.3. Network Address Translation Characteristics of ICQ
        • 19.2.4. Summary of Recommendations for ICQ
      • 19.3. talk
        • 19.3.1. Packet Filtering Characteristics of talk
        • 19.3.2. Proxying Characteristics of talk
        • 19.3.3. Network Address Translation Characteristics of talk
        • 19.3.4. Summary of Recommendations for talk
      • 19.4. Multimedia Protocols
        • 19.4.1. T.120 and H.323
          • 19.4.1.1. Packet filtering characteristics of T.120
          • 19.4.1.2. Proxying characteristics of T.120
          • 19.4.1.3. Network address translation characteristics of T.120
          • 19.4.1.4. Packet filtering characteristics of H.323
          • 19.4.1.5. Proxying characteristics of H.323
          • 19.4.1.6. Network address translation characteristics of H.323
          • 19.4.1.7. Summary of recommendations for T.120 and H.323
        • 19.4.2. The Real-Time Transport Protocol (RTP) and the RTP Control Protocol (RTCP)
          • 19.4.2.1. Packet filtering characteristics of RTP and RTCP
          • 19.4.2.2. Proxying characteristics of RTP and RTCP
          • 19.4.2.3. Network address translation of RTP and RTCP
          • 19.4.2.4. Summary of recommendations for RTP and RTCP
      • 19.5. NetMeeting
        • 19.5.1. Packet Filtering Characteristics of NetMeeting
        • 19.5.2. Proxying Characteristics of NetMeeting
        • 19.5.3. Network Address Translation Characteristics of NetMeeting
        • 19.5.4. Summary of Recommendations for NetMeeting
      • 19.6. Multicast and the Multicast Backbone (MBONE)
        • 19.6.1. Summary of Recommendations for Multicast
    • 20. Naming and Directory Services
      • 20.1. Domain Name System (DNS)
        • 20.1.1. Packet Filtering Characteristics of DNS
        • 20.1.2. Proxying Characteristics of DNS
        • 20.1.3. DNS Data
        • 20.1.4. DNS Security Problems
          • 20.1.4.1. Bogus answers to DNS queries
          • 20.1.4.2. Malicious DNS queries
          • 20.1.4.3. Mismatched data between the hostname and IP address DNS trees
          • 20.1.4.4. Dynamic update
          • 20.1.4.5. Revealing too much information to attackers
        • 20.1.5. Setting Up DNS to Hide Information, Without Subdomains
          • 20.1.5.1. Set up a "fake" DNS server on the bastion host for the outside world to use
          • 20.1.5.2. Set up a real DNS server on an internal system for internal hosts to use
          • 20.1.5.3. Internal DNS clients query the internal server
          • 20.1.5.4. Bastion DNS clients also query the internal server
          • 20.1.5.5. What your packet filtering system needs to allow
        • 20.1.6. Setting Up DNS to Hide Information, with Subdomains
        • 20.1.7. Setting Up DNS Without Hiding Information
        • 20.1.8. Windows 2000 and DNS
        • 20.1.9. Network Address Translation Characteristics of DNS
        • 20.1.10. Summary of Recommendations for DNS
      • 20.2. Network Information Service (NIS)
        • 20.2.1. Summary of Recommendations for NIS
      • 20.3. NetBIOS for TCP/IP Name Service and Windows Internet Name Service
        • 20.3.1. Name Resolution Under Windows
        • 20.3.2. NetBIOS Names
        • 20.3.3. NetBT Name Service Operations
          • 20.3.3.1. General principles of NetBT operations
          • 20.3.3.2. Name registration
          • 20.3.3.3. Name refresh
          • 20.3.3.4. Name resolution
          • 20.3.3.5. Name release
          • 20.3.3.6. Conflict management
        • 20.3.4. WINS Server-Server Communication
        • 20.3.5. The WINS Manager
        • 20.3.6. Security Implications of NetBT Name Service and WINS
        • 20.3.7. Packet Filtering Characteristics of NetBT Name Service
        • 20.3.8. Proxying Characteristics of NetBT Name Service and WINS
        • 20.3.9. Network Address Translation Characteristics of NetBT Name Service and WINS
        • 20.3.10. Summary of Recommendations for NetBT Name Service and WINS
      • 20.4. The Windows Browser
        • 20.4.1. Domains and Workgroups
        • 20.4.2. Windows Browser Roles
          • 20.4.2.1. Domain master browser
          • 20.4.2.2. Master browser
          • 20.4.2.3. Backup browsers
          • 20.4.2.4. Potential browsers
          • 20.4.2.5. Browseable server
          • 20.4.2.6. Browser client
        • 20.4.3. Browser Elections
        • 20.4.4. Security Implications of the Windows Browser
        • 20.4.5. Packet Filtering Characteristics of the Windows Browser
        • 20.4.6. Proxying Characteristics of the Windows Browser
        • 20.4.7. Network Address Translation Characteristics of the Windows Browser
        • 20.4.8. Summary of Recommendations for the Windows Browser
      • 20.5. Lightweight Directory Access Protocol (LDAP)
        • 20.5.1. LDAPS
        • 20.5.2. Packet Filtering Characteristics of LDAP
        • 20.5.3. Proxying Characteristics of LDAP
        • 20.5.4. Network Address Translation Characteristics of LDAP
        • 20.5.5. Summary of Recommendations for LDAP
      • 20.6. Active Directory
      • 20.7. Information Lookup Services
        • 20.7.1. finger
          • 20.7.1.1. Packet filtering characteristics of finger
          • 20.7.1.2. Proxying characteristics of finger
          • 20.7.1.3. Network address translation characteristics of finger
          • 20.7.1.4. Summary of recommendations for finger
        • 20.7.2. whois
          • 20.7.2.1. Packet filtering characteristics of whois
          • 20.7.2.2. Proxying characteristics of whois
          • 20.7.2.3. Network address translation characteristics of whois
          • 20.7.2.4. Summary of recommendations for whois
    • 21. Authentication and Auditing Services
      • 21.1. What Is Authentication?
        • 21.1.1. Something You Are
        • 21.1.2. Something You Know
        • 21.1.3. Something You Have
      • 21.2. Passwords
      • 21.3. Authentication Mechanisms
        • 21.3.1. One-Time Password Software
        • 21.3.2. One-Time Password Hardware
      • 21.4. Modular Authentication for Unix
        • 21.4.1. The TIS FWTK Authentication Server
          • 21.4.1.1. Problems with the authentication server
        • 21.4.2. Pluggable Authentication Modules (PAM)
      • 21.5. Kerberos
        • 21.5.1. How It Works
        • 21.5.2. Extending Trust
        • 21.5.3. Packet Filtering Characteristics of Kerberos
        • 21.5.4. Proxying and Network Address Translation Characteristics of Kerberos
        • 21.5.5. Summary of Recommendations for Kerberos
      • 21.6. NTLM Domains
        • 21.6.1. Finding a Domain Controller
        • 21.6.2. The Logon Process
        • 21.6.3. Secure Channel Setup
        • 21.6.4. SMB Authentication
        • 21.6.5. Accessing Other Computers
        • 21.6.6. Alternate Authentication Methods
        • 21.6.7. Controller-to-Controller Communication
        • 21.6.8. The User Manager
        • 21.6.9. Packet Filtering, Proxying, and Network Address Translation Characteristics of NTLM Domain Authentication
        • 21.6.10. Summary of Recommendations for NTLM Domain Authentication
      • 21.7. Remote Authentication Dial-in User Service (RADIUS)
        • 21.7.1. Packet Filtering Characteristics of RADIUS
        • 21.7.2. Proxying Characteristics of RADIUS
        • 21.7.3. Network Address Translation Characteristics of RADIUS
        • 21.7.4. Summary of Recommendations for RADIUS
      • 21.8. TACACS and Friends
        • 21.8.1. Packet Filtering Characteristics of TACACS and Friends
        • 21.8.2. Proxying Characteristics of TACACS and Friends
        • 21.8.3. Network Address Translation Characteristics of TACACS and Friends
        • 21.8.4. Summary of Recommendations for TACACS and Friends
      • 21.9. Auth and identd
        • 21.9.1. Packet Filtering Characteristics of Auth
        • 21.9.2. Proxying Characteristics of Auth
        • 21.9.3. Network Address Translation Characteristics of Auth
        • 21.9.4. Summary of Recommendations for Auth
    • 22. Administrative Services
      • 22.1. System Management Protocols
        • 22.1.1. syslog
          • 22.1.1.1. Packet filtering characteristics of syslog
          • 22.1.1.2. Proxying characteristics of syslog
          • 22.1.1.3. Network address translation and syslog
          • 22.1.1.4. Summary of recommendations for syslog
        • 22.1.2. Simple Network Management Protocol (SNMP)
          • 22.1.2.1. SNMP version 3
          • 22.1.2.2. Packet filtering characteristics of SNMP
          • 22.1.2.3. Proxying characteristics of SNMP
          • 22.1.2.4. Network address translation and SNMP
        • 22.1.3. System Management Server (SMS)
        • 22.1.4. Performance Monitor and Network Monitor
        • 22.1.5. Summary Recommendations for System Management
      • 22.2. Routing Protocols
        • 22.2.1. Routing Information Protocol (RIP)
          • 22.2.1.1. Packet filtering characteristics of RIP
        • 22.2.2. Open Shortest Path First (OSPF)
          • 22.2.2.1. Packet filtering characteristics of OSPF
        • 22.2.3. Internet Group Management Protocol (IGMP)
          • 22.2.3.1. Packet filtering characteristics of IGMP
        • 22.2.4. Router Discovery/ICMP Router Discovery Protocol (IRDP)
          • 22.2.4.1. Packet filtering characteristics of router discovery
        • 22.2.5. Proxying Characteristics of Routing Protocols
        • 22.2.6. Network Address Translation Characteristics of Routing Protocols
        • 22.2.7. Summary of Recommendations for Routing Protocols
      • 22.3. Protocols for Booting and Boot-Time Configuration
        • 22.3.1. bootp
        • 22.3.2. Dynamic Host Configuration Protocol (DHCP)
        • 22.3.3. Packet Filtering Characteristics of DHCP and bootp
        • 22.3.4. Proxying Characteristics of bootp and DHCP
        • 22.3.5. Network Address Translation Characteristics of Booting and Boot-Time Configuration
        • 22.3.6. Summary of Recommendations for Booting and Boot-Time Configuration
      • 22.4. ICMP and Network Diagnostics
        • 22.4.1. ping
          • 22.4.1.1. Packet filtering characteristics of ping
          • 22.4.1.2. Proxying characteristics of ping
          • 22.4.1.3. Network address translation and ping
        • 22.4.2. traceroute
          • 22.4.2.1. Packet filtering characteristics of traceroute
          • 22.4.2.2. Proxying characteristics of traceroute
          • 22.4.2.3. Network address translation and traceroute
        • 22.4.3. Other ICMP Packets
          • 22.4.3.1. Packet filtering characteristics of ICMP
        • 22.4.4. Summary of Recommendations for ICMP
      • 22.5. Network Time Protocol (NTP)
        • 22.5.1. Packet Filtering Characteristics of NTP
        • 22.5.2. Proxying Characteristics of NTP
        • 22.5.3. Network Address Translation Characteristics of NTP
        • 22.5.4. Configuring NTP to Work with a Firewall
        • 22.5.5. Summary of Recommendations for NTP
      • 22.6. File Synchronization
        • 22.6.1. rdist
        • 22.6.2. rsync
          • 22.6.2.1. Packet filtering characteristics of rsync
          • 22.6.2.2. Proxying characteristics of rsync
          • 22.6.2.3. Network address translation characteristics of rsync
        • 22.6.3. Windows NT Directory Replication
        • 22.6.4. Windows 2000 File Replication Service (FRS)
        • 22.6.5. Summary of Recommendations for File Synchronization
      • 22.7. Mostly Harmless Protocols
        • 22.7.1. Packet Filtering Characteristics of Mostly Harmless Protocols
        • 22.7.2. Proxying Characteristics of Mostly Harmless Protocols
        • 22.7.3. Network Address Translation Characteristics of Mostly Harmless Protocols
        • 22.7.4. Summary Recommendations for Mostly Harmless Protocols
    • 23. Databases and Games
      • 23.1. Databases
        • 23.1.1. Locating Database Servers
          • 23.1.1.1. Putting both the web server and the database on the perimeter network
          • 23.1.1.2. Putting both the web server and the database on the internal network
          • 23.1.1.3. Using the database's protocols to connect to a perimeter web server
          • 23.1.1.4. Using a custom protocol to connect to a perimeter web server
        • 23.1.2. Open Database Connectivity (ODBC) and Java Database Connectivity ( JDBC)
        • 23.1.3. Oracle SQL*Net and Net8
          • 23.1.3.1. Security implications of SQL*Net and Net8
          • 23.1.3.2. Packet filtering characteristics of SQL*Net and Net8
          • 23.1.3.3. Proxying characteristics of SQL*Net and Net8
          • 23.1.3.4. Network address translation characteristics of SQL*Net and Net8
          • 23.1.3.5. Summary of recommendations for SQL*Net and Net8
        • 23.1.4. Tabular Data Stream (TDS)
        • 23.1.5. Sybase
          • 23.1.5.1. Packet filtering characteristics of Sybase
          • 23.1.5.2. Proxying characteristics of Sybase
          • 23.1.5.3. Network address translation characteristics of Sybase
          • 23.1.5.4. Summary of recommendations for Sybase
        • 23.1.6. Microsoft SQL Server
          • 23.1.6.1. Packet filtering characteristics of Microsoft SQL Server
          • 23.1.6.2. Proxying characteristics of Microsoft SQL Server
          • 23.1.6.3. Network address translation and Microsoft SQL Server
          • 23.1.6.4. Summary of recommendations for Microsoft SQL Server
      • 23.2. Games
        • 23.2.1. Quake
        • 23.2.2. Summary of Recommendations for Games
    • 24. Two Sample Firewalls
      • 24.1. Screened Subnet Architecture
        • 24.1.1. Service Configuration
          • 24.1.1.1. HTTP and HTTPS
          • 24.1.1.2. SMTP
          • 24.1.1.3. Telnet
          • 24.1.1.4. SSH
          • 24.1.1.5. FTP
          • 24.1.1.6. NNTP
          • 24.1.1.7. DNS
        • 24.1.2. Packet Filtering Rules
          • 24.1.2.1. Interior router
          • 24.1.2.2. Exterior router
        • 24.1.3. Other Configuration Work
        • 24.1.4. Analysis
          • 24.1.4.1. Least privilege
          • 24.1.4.2. Defense in depth
          • 24.1.4.3. Choke point
          • 24.1.4.4. Weakest link
          • 24.1.4.5. Fail-safe stance
          • 24.1.4.6. Universal participation
          • 24.1.4.7. Diversity of defense
          • 24.1.4.8. Simplicity
        • 24.1.5. Conclusions
      • 24.2. Merged Routers and Bastion Host Using General-Purpose Hardware
        • 24.2.1. Service Configuration
          • 24.2.1.1. HTTP and HTTPS
          • 24.2.1.2. SMTP
          • 24.2.1.3. Telnet
          • 24.2.1.4. SSH
          • 24.2.1.5. FTP
          • 24.2.1.6. NNTP
          • 24.2.1.7. DNS
        • 24.2.2. Packet Filtering Rules
        • 24.2.3. Other Configuration Work
        • 24.2.4. Analysis
          • 24.2.4.1. Least privilege
          • 24.2.4.2. Defense in depth
          • 24.2.4.3. Choke point
          • 24.2.4.4. Weakest link
          • 24.2.4.5. Fail-safe stance
          • 24.2.4.6. Universal participation
          • 24.2.4.7. Diversity of defense
          • 24.2.4.8. Simplicity
        • 24.2.5. Conclusions
  • IV. Keeping Your Site Secure
    • 25. Security Policies
      • 25.1. Your Security Policy
        • 25.1.1. What Should a Security Policy Contain?
          • 25.1.1.1. Explanations
          • 25.1.1.2. Everybody's responsibilities
          • 25.1.1.3. Regular language
          • 25.1.1.4. Enforcement authority
          • 25.1.1.5. Provision for exceptions
          • 25.1.1.6. Provision for reviews
          • 25.1.1.7. Discussion of specific security issues
        • 25.1.2. What Should a Security Policy Not Contain?
          • 25.1.2.1. Technical details
          • 25.1.2.2. Somebody else's problems
          • 25.1.2.3. Problems that aren't computer security problems
      • 25.2. Putting Together a Security Policy
        • 25.2.1. What Is Your Security Policy?
        • 25.2.2. What Is Your Site's Security Policy?
        • 25.2.3. External Factors That Influence Security Policies
      • 25.3. Getting Strategic and Policy Decisions Made
        • 25.3.1. Enlist Allies
        • 25.3.2. Involve Everybody Who's Affected
        • 25.3.3. Accept "Wrong" Decisions
        • 25.3.4. Present Risks and Benefits in Different Ways for Different People
        • 25.3.5. Avoid Surprises
        • 25.3.6. Condense to Important Decisions, with Implications
        • 25.3.7. Justify Everything Else in Terms of Those Decisions
        • 25.3.8. Emphasize that Many Issues Are Management and Personnel Issues, not Technical Issues
        • 25.3.9. Don't Assume That Anything Is Obvious
      • 25.4. What If You Can't Get a Security Policy?
    • 26. Maintaining Firewalls
      • 26.1. Housekeeping
        • 26.1.1. Backing Up Your Firewall
        • 26.1.2. Managing Your Accounts
        • 26.1.3. Managing Your Disk Space
      • 26.2. Monitoring Your System
        • 26.2.1. Special-Purpose Monitoring Devices
        • 26.2.2. Intrusion Detection Systems
        • 26.2.3. What Should You Watch For?
        • 26.2.4. The Good, the Bad, and the Ugly
        • 26.2.5. Responding to Probes
        • 26.2.6. Responding to Attacks
      • 26.3. Keeping up to Date
        • 26.3.1. Keeping Yourself up to Date
          • 26.3.1.1. Mailing lists
          • 26.3.1.2. Newsgroups
          • 26.3.1.3. Web sites
          • 26.3.1.4. Professional forums
        • 26.3.2. Keeping Your Systems up to Date
      • 26.4. How Long Does It Take?
      • 26.5. When Should You Start Over?
    • 27. Responding to Security Incidents
      • 27.1. Responding to an Incident
        • 27.1.1. Evaluate the Situation
        • 27.1.2. Start Documenting
        • 27.1.3. Disconnect or Shut Down, as Appropriate
        • 27.1.4. Analyze and Respond
        • 27.1.5. Make "Incident in Progress" Notifications
          • 27.1.5.1. Your own organization
          • 27.1.5.2. CERT-CC or other incident response teams
          • 27.1.5.3. Vendors and service providers
          • 27.1.5.4. Other sites
        • 27.1.6. Snapshot the System
        • 27.1.7. Restore and Recover
        • 27.1.8. Document the Incident
      • 27.2. What to Do After an Incident
      • 27.3. Pursuing and Capturing the Intruder
      • 27.4. Planning Your Response
        • 27.4.1. Planning for Detection
        • 27.4.2. Planning for Evaluation of the Incident
        • 27.4.3. Planning for Disconnecting or Shutting Down Machines
        • 27.4.4. Planning for Notification of People Who Need to Know
          • 27.4.4.1. Your own organization
          • 27.4.4.2. CERT-CC and other incident response teams
          • 27.4.4.3. Vendors and service providers
          • 27.4.4.4. Other sites
        • 27.4.5. Planning for Snapshots
        • 27.4.6. Planning for Restoration and Recovery
        • 27.4.7. Planning for Documentation
        • 27.4.8. Periodic Review of Plans
      • 27.5. Being Prepared
        • 27.5.1. Backing Up Your Filesystems
        • 27.5.2. Labeling and Diagramming Your System
        • 27.5.3. Keeping Secured Checksums
        • 27.5.4. Keeping Activity Logs
        • 27.5.5. Keeping a Cache of Tools and Supplies
        • 27.5.6. Testing the Reload of the Operating System
        • 27.5.7. Doing Drills
  • V. Appendixes
    • A. Resources
      • A.1. Web Pages
        • A.1.1. Telstra
        • A.1.2. CERIAS
        • A.1.3. The Linux Documentation Project
        • A.1.4. The Linux Router Project
      • A.2. FTP Sites
        • A.2.1. cerias.purdue.edu
        • A.2.2. info.cert.org
      • A.3. Mailing Lists
        • A.3.1. Firewalls
        • A.3.2. Firewall Wizards
        • A.3.3. FWTK-USERS
        • A.3.4. BugTraq
        • A.3.5. NTBugTraq
        • A.3.6. CERT-Advisory
        • A.3.7. RISKS
      • A.4. Newsgroups
      • A.5. Response Teams
        • A.5.1. CERT-CC
        • A.5.2. FIRST
        • A.5.3. NIST CSRC
      • A.6. Other Organizations
        • A.6.1. Internet Engineering Task Force (IETF)
        • A.6.2. World Wide Web Consortium (W3C)
        • A.6.3. USENIX Association
        • A.6.4. System Administrators Guild (SAGE)
        • A.6.5. System Administration, Networking, and Security (SANS) Institute
      • A.7. Conferences
        • A.7.1. USENIX Association Conferences
          • A.7.1.1. USENIX Unix Security Symposium
          • A.7.1.2. USENIX System Administration (LISA) Conference
          • A.7.1.3. USENIX Large Installation System Administration of Windows NT (LISA-NT) Conference
          • A.7.1.4. USENIX Technical Conferences
        • A.7.2. Unix System Administration, Networking, and Security (SANS) Conference
        • A.7.3. Internet Society Symposium on Network and Distributed System Security (SNDSS)
      • A.8. Papers
      • A.9. Books
    • B. Tools
      • B.1. Authentication Tools
        • B.1.1. TIS Internet Firewall Toolkit (FWTK)
        • B.1.2. Kerberos
      • B.2. Analysis Tools
        • B.2.1. COPS
        • B.2.2. Tiger
        • B.2.3. Tripwire
        • B.2.4. SATAN
        • B.2.5. SAINT
      • B.3. Packet Filtering Tools
        • B.3.1. ipfilter
      • B.4. Proxy Systems Tools
        • B.4.1. TIS Internet Firewall Toolkit (FWTK)
        • B.4.2. SOCKS
        • B.4.3. UDP Packet Relayer
        • B.4.4. tircproxy
      • B.5. Daemons
        • B.5.1. wuarchive ftpd
        • B.5.2. GateD
        • B.5.3. Zebra
        • B.5.4. Postfix
        • B.5.5. qmail
        • B.5.6. smail
        • B.5.7. portmap
        • B.5.8. Andrew File System (AFS)
        • B.5.9. rsync
        • B.5.10. Samba
        • B.5.11. ssh
        • B.5.12. BO2K
        • B.5.13. mIRC
      • B.6. Utilities
        • B.6.1. TIS Internet Firewall Toolkit (FWTK)
        • B.6.2. TCP Wrapper
        • B.6.3. chrootuid
        • B.6.4. inzider
        • B.6.5. MRTG
        • B.6.6. NOCOL
        • B.6.7. NetCat
        • B.6.8. NetSaint
        • B.6.9. PGP
        • B.6.10. trimlog
        • B.6.11. AntiSniff
        • B.6.12. tcpdump
    • C. Cryptography
      • C.1. What Are You Protecting and Why?
      • C.2. Key Components of Cryptographic Systems
        • C.2.1. Encryption
          • C.2.1.1. Kinds of encryption algorithms
          • C.2.1.2. Encryption algorithms and key length
        • C.2.2. Cryptographic Hashes, Checksums, and Message Digests
        • C.2.3. Integrity Protection
        • C.2.4. Random Numbers
      • C.3. Combined Cryptography
        • C.3.1. Digital Signatures
        • C.3.2. Certificates
        • C.3.3. Certificate Trust Models
        • C.3.4. Key Distribution and Exchange
      • C.4. What Makes a Protocol Secure?
        • C.4.1. Selecting an Algorithm
        • C.4.2. Mutual Authentication
        • C.4.3. Sharing a Secret
        • C.4.4. Identifying Altered Messages
        • C.4.5. Destroying the Shared Secret
      • C.5. Information About Algorithms
        • C.5.1. Encryption Algorithms
        • C.5.2. Digital Signature Algorithms
        • C.5.3. Cryptographic Hashes and Message Digests
        • C.5.4. Key Exchange
        • C.5.5. Key Sizes and Strength
        • C.5.6. Evaluating Other Algorithms
  • Index
  • About the Authors
  • Colophon
  • SPECIAL OFFER: Upgrade this ebook with OReilly

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