Firewall Fundamentals, 1st edition
Published by Cisco Press (June 2, 2006) © 2006
- Wes Noonan
- Ido Dubrawsky
- A print text (hardcover or paperback)Â
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- Also available for purchase as an ebook from all major ebook resellers, including InformIT.com
The essential guide to understanding and using firewalls to protect personal computers and your network
- An easy-to-read introduction to the most commonly deployed network security device
- Understand the threats firewalls are designed to protect against
- Learn basic firewall architectures, practical deployment scenarios, and common management and troubleshooting tasks
- Includes configuration, deployment, and management checklists
Increasing reliance on the Internet in both work and home environments has radically increased the vulnerability of computing systems to attack from a wide variety of threats. Firewall technology continues to be the most prevalent form of protection against existing and new threats to computers and networks. A full understanding of what firewalls can do, how they can be deployed to maximum effect, and the differences among firewall types can make the difference between continued network integrity and complete network or computer failure. Firewall Fundamentals introduces readers to firewall concepts and explores various commercial and open source firewall implementations--including Cisco, Linksys, and Linux--allowing network administrators and small office/home office computer users to effectively choose and configure their devices. Firewall Fundamentals is written in clear and easy-to-understand language and helps novice users understand what firewalls are and how and where they are used. It introduces various types of firewalls, first conceptually and then by explaining how different firewall implementations actually work. It also provides numerous implementation examples, demonstrating the use of firewalls in both personal and business-related scenarios, and explains how a firewall should be installed and configured. Additionally, generic firewall troubleshooting methodologies and common management tasks are clearly defined and explained.
     Introduction
Part 1Â Â Â Â Â 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 IIÂ Â Â Â 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 IIIÂ Â Â 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 IVÂ Â Â Â Appendixes
Appendix A Firewall and Security Tools
Appendix B Firewall and Security Resources
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Wesley J Noonan (Houston, Texas) has been working in the computer industry for over 12 years, specializing in Windows-based networks and network infrastructure security design and implementation. He is a Staff Quality Engineer for NetIQ working on their security solutions product line.
Ido Dubrawsky (Sliver Springs, MD) is a Senior Security Consultant with Callisma, an SBC subsidiary. He advises customers on a wide variety of security issues. Previously he was a Network Security Architect with Cisco Systems SAFE Architecture Team
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