Customer Reviews

Troubleshooting Linux® Firewalls

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The Shinn brothers are legendary in information security, so when I saw this book, I made sure to put it on the top of my airline reading list.

If you ever watch someone closely that is trying to troubleshoot a computer, network, or firewall, you quickly realize fault detection and root cause determination are skills very few people have. I watch people change two things and reboot, or try the last thing they just tried again and just shake my head.

The book is not just about troubleshooting, it includes setup, network theory, and proper design as well. However, chapter 4 should be required reading for anyone that is allowed near a computer with privileged access, windows or unix. If this book gets revised I would love to see the troubleshooting chapter expanded, that is critially important information.

Despite a number of introductory chapters, there is not much fluff in here. It provides a sound treatment of architectural issues before getting down to business with netfilter and iptables. It touches on some diagnostics techniques and tools before dealing with firewall configurations that are specific to popular services. This is a very useful book for firewall administrators. The index could be better, but I've been able to find what I needed.

Chapters in this 360 page volume include:
-Introduction
-Getting Started
-Local Firewall Security
-Troubleshooting Methodology
-The OSI Model
-netfilter and iptables Overview
-Using iptables
-A Tour of Our Collective Toolbox
-Diagnostics
-Testing Your Firewall Rules for Security
-Layer 2/Inline Filtering
-NAT and IP Forwarding
-General IP
-SMTP
-Web Services
-File Services
-Instant Messaging
-DNS/DHCP
-VPNs

Linux firewalls are attractive to many companies because of their free nature. But free does not mean easy to understand or use. It is this need to which the book is addressed.

The authors show that linux comes with powerful, versatile firewall and intrusion detection utilities. But if you need a firewall, chances are you want it to work as best as possible in defending your subnet. So details of optimum usage matter. Starting from the top down, with an analysis of how to devise a network security plan, to implementing it in a secure firewall.

The book talks about how to best use various tools like nmap and iptables. Your linux toolbox is your arsenal. The problem is that some tools are not the easiest to use. Not helped by the fact that most are run at the command line. The latter is desirable for maximum flexibility, especially in writing scripts that use them. The book has guidelines for best practices.

The chapter on VPN is concise and accurate. But this topic is important enough in its own right that if you plan on setting one up, seriously consider getting a book devoted to it.