Contents

• List of Figures
• Preface
  • Purpose
  • Audience
  • Document Structure
  • Terminology
  • Background
  • Solutions
  • Recommendations
• Introduction to the Internet and Internet Security
  • The Internet
    • Common Services
    • Internet Hosts
  • Overview of TCP/IP Internals
    • IP
    • TCP
    • UDP
    • ICMP
    • TCP and UDP Port Structure
  • Security-Related Problems
    • Security Incidents on the Internet
    • Weak Authentication
    • Ease of Spying/Monitoring
    • Ease of Spoofing
    • Flawed LAN Services and Mutually Trusting Hosts
    • Complex Configuration and Controls
    • Host-based Security Does Not Scale
  • How Vulnerable Are Internet Sites?
• Introduction to Firewalls
  • The Firewall Concept
  • Why Firewalls
    • Protection from Vulnerable Services
    • Controlled Access to Site Systems
    • Concentrated Security
    • Enhanced Privacy
    • Logging and Statistics on Network Use, Misuse
    • Policy Enforcement
  • Issues and Problems with Firewalls
    • Restricted Access to Desirable Services
    • Large Potential for Back Doors
    • Little Protection from Insider Attacks
    • Other Issues
  • Firewall Components
    • Network Policy
    • Service Access Policy
    • Firewall Design Policy
    • Advanced Authentication
    • Packet Filtering
    • Which Protocols to Filter
    • Problems with Packet Filtering Routers
    • Application Gateways
    • Circuit-Level Gateways
• Putting the Pieces Together: Firewall Examples
  • Packet Filtering Firewall
  • Dual-homed Gateway Firewall
  • Screened Host Firewall
  • Screened Subnet Firewall
  • Integrating Modem Pools with Firewalls
• Next Steps
  • Firewall Policy
    • Steps in Creating a Service Access Policy
    • Flexibility in Policy
    • Remote User Advanced Authentication Policy
    • Dial-in/out Policy
    • Remote Network Connections
    • Information Server Policy
  • Procuring a Firewall
    • What Should a Firewall Contain?
    • To Buy or Build a Firewall
  • Administration Issues with Firewalls
    • System Management Expertise
    • Site System Administration
    • Incident Handling Contacts
• References
• On-Line Sources for More Information
• Firewall-Specific Information
• NIST Computer Security Resource Clearinghouse
• Forum of Incident Response and Security Teams
• Internet Firewalls Frequently Asked Questions
  • Internet Firewalls Frequently Asked Questions
• About this document ...