Firewall Fundamentals

Introduction

Part 1 Introduction to Firewalls3

Chapter 1 Introduction to Firewalls

What Is a Firewall?

What Can Firewalls Do?

Firewalls Manage and Control Network Traffic

Firewalls Authenticate Access

Firewalls Act as an Intermediary

Firewalls Protect Resources

Firewalls Record and Report on Events

What Are the Threats?

Targeted Versus Untargeted Attacks

Viruses, Worms, and Trojans

Malicious Content and Malware

Denial of Service

Zombies

Compromise of Personal Information and Spyware

Social Engineering

New Attack Vectors

Insecure/Poorly Designed Applications

What Are the Motives?

Security Policies

Examples of Security Policies

Firewalls and Trust

Determining If You Need a Firewall

Summary

Chapter 2 Firewall Basics

Firewall Taxonomy

Personal Firewalls

Network Firewalls

Firewall Products

Software Firewalls

Appliance Firewalls

Integrated Firewalls

Firewall Technologies

Personal Firewalls

Packet Filters

NAT Firewalls

Circuit-Level Firewalls

Proxy Firewalls

Stateful Firewalls

Transparent Firewalls

Virtual Firewalls

Open and Closed Source Firewalls

Summary

Chapter 3 TCP/IP for Firewalls

Protocols, Services, and Applications

The OSI Model

The Department of Defense (DoD) Model

How Firewalls Use Protocols, Applications, and Services

Internet Protocol (IP)

IP Packet Structure

The IP Packet Header

Bad IP Packets

Transmission Control Protocol (TCP)

TCP Segment Structure

TCP Segment Header

Bad TCP

User Datagram Protocol (UDP)

UDP Message Structure

UDP Datagram Header

Bad UDP

Internet Control Message Protocol (ICMP)

ICMP Message Structure

Bad ICMP

Addressing in IP Networks

Physical Addresses

Logical Addresses

IP Addressing

Subnets

IPv6

Network Address Translation (NAT)

NAT Implementations

NAT and IPsec: The Issues and the Solutions

Broadcast and Multicast

IP Services

IP Routing

Types of Routing

How the IP Routing Process Works

Different Classes of Routing Protocols

Common Routing Protocols

Applications Using IP

Common Applications Using IP

Less-Common Applications Using IP

Protocols Used to Implement Security

Summary

Part II How Firewalls Work

Chapter 4 Personal Firewalls: Windows Firewall and Trend Micro's PC-cillin

Windows Firewall and Windows XP

How Windows Firewall Works

Configuring Windows Firewall

Windows Firewall Features

Windows Firewall Checklist

Trend Micro's PC-cillin Firewall Feature

PC-cillin Requirements

How the Trend Micro Firewall Works

Configuring the Trend Micro Firewall

Trend Micro Firewall Features

Trend Micro Firewall Checklist

Summary

Chapter 5 Broadband Routers and Firewalls

How Broadband Routers and Firewalls Work

Linksys Broadband Routers/Firewalls

Security and Filtering Features

Routing Features

Management and Administration Features

Miscellaneous Features

Linksys Requirements

How the Linksys Router/Firewall Works

Filtering Traffic from External Sources

Filtering Traffic from Internal Sources

Configuring Linksys

Configuring Basic Setup

Configuring Security

Configuring Applications & Gaming

Configuring Administration

Linksys Checklist

Summary

Chapter 6 Cisco PIX Firewall and ASA Security Appliance

PIX/ASA Features

Choosing Between the PIX and the ASA

Cisco PIX Firewall and ASA Models

SOHO Solution

Medium- to Large-Office Solution

Enterprise Office and Service Provider Solution

How the PIX/ASA Firewall Works

Firewall Security Policy

Firewall Modes of Operation

Stateful Inspection

Configuring the Cisco PIX/ASA

Assigning IP Addresses to the Firewall Interfaces

Configuring the Firewall Name, Domain Name, and Passwords

Configuring the Firewall Routing Settings

Configuring the Firewall for Remote Management Access

Configuring NAT Settings for Outbound Access

Configuring the ACLs

Configuring Logging on the Firewall

PIX/ASA Checklist

Summary

Chapter 7 Linux-Based Firewalls

NetFilter Features

NetFilter Requirements

How NetFilter Works

Configuring NetFilter

IPTables Command-Line Tool

Firewall Builder

Firestarter

Webmin

NetFilter Checklist

Summary

Chapter 8 Application Proxy Firewalls

Application Layer Filtering

How Application Filtering Works

The Difference Between Application Filtering and Deep Packet Inspection

Proxy Server Functionality

Limitations of Application Proxy Firewalls

Microsoft ISA Server 2004 Firewall

Microsoft ISA Server 2004 Features

Microsoft ISA Server 2004 Requirements and Preparation

How the Microsoft ISA Server 2004 Firewall Works

Microsoft ISA Server 2004 Checklist

Summary

Chapter 9 Where Firewalls Fit in a Network

Different Types of Office Requirements

Central Office

Remote Office

Single-Firewall Architectures

Internet Firewall with a Single DMZ

Internet Firewall with Multiple DMZs

Internet-Screening Firewall (No DMZ)

Dual-Firewall Architecture

The Firewall System

Single-Firewall System

Dual-Firewall System

Where Personal/Desktop Firewalls Fit in a Network

Where Application Firewalls Fit in a Network

Firewalls and VLANs

Virtual Firewalls

Using Firewalls to Segment Internal Resources

Protecting Sensitive Internal Resources

Protecting from WAN or Remote-Access Requests

Protecting Individual Internal Resources

Be Realistic When Implementing Internal Firewalls

High-Availability Firewall Designs

Summary

Part III Managing and Maintaining Firewalls

Chapter 10 Firewall Security Policies

Written Security Policies

The Difference Between Policies, Standards, Guidelines, and Procedures

Security Policy Format

Common Security Policies

Firewall Security Policy

Firewall Policies/Rulesets

Ingress Filters

Egress Filters

Management-Access Ruleset

Summary

Chapter 11 Managing Firewalls

Default Passwords

Maintaining the Underlying Platform

Firewall Management Interface

Managing Firewalls with a CLI

Managing Firewalls with a GUI

Interface Preference

Management Access

In-Band Management

Out-of-Band Management

Telnet vs. SSH

HTTP vs. HTTPS

Common Firewall Management Tasks

Initial Configuration

Modifying the Configuration

Updating the Firewall Software

Summary

Chapter 12 What Is My Firewall Telling Me?

Firewalls and Logging

The Syslog Protocol

Proprietary Logging Methods

Why Logging Is Important

Firewall Log Review and Analysis

What to Look for in Firewall Logs

Cisco Secure PIX Firewall Syslog Event Baseline

Firewall Forensics

The Value (or Not) of IP Addresses

Deciphering Port Numbers

Securing the Firewall

Summary

Chapter 13 Troubleshooting Firewalls

Developing a Troubleshooting Checklist

Step 1: Verify the Problem Reported

Step 2: Test Connectivity

Step 3: Physically Check the Firewall

Step 4: Check for Recent Changes

Step 5: Check the Firewall Logs for Errors

Step 6: Verify the Firewall Configuration

Step 7: Verify the Firewall Ruleset

Step 8: Verify That Any Dependent, Non-Firewall-Specific
Systems Are Not the Culprit

Step 9: Monitor the Network Traffic

Basic Firewall Troubleshooting

Troubleshooting Connectivity Through the Firewall

Troubleshooting Connectivity to the Firewall

Advanced Firewall Troubleshooting

Troubleshooting Example

Summary

Chapter 14 Going Beyond Basic Firewall Features

Content Filtering

Implementing a URL Filter

Maintaining URL Filters

What to Do If. . .

Performing Application Filtering

Applications That Are Hard to Firewall

Intrusion Detection and Prevention

Overview of IDS

Virtual Private Networks

IPsec VPNs

SSL VPNs

Summary

Endnotes

Part IV Appendixes

Appendix A Firewall and Security Tools

Appendix B Firewall and Security Resources



1587052210TOC052206