System administrators need to stay ahead of new security
vulnerabilities that leave their networks exposed every day. A
firewall and an intrusion detection system (IDS) are two important
weapons in that fight, enabling you to proactively deny access and
monitor network traffic for signs of an attack.
Linux Firewalls discusses the technical details of the iptables
firewall and the Netfilter framework that are built into the Linux
kernel, and it explains how they provide strong filtering, Network
Address Translation (NAT), state tracking, and application layer
inspection capabilities that rival many commercial tools.
You'll learn how to deploy iptables as an IDS with psad and
fwsnort and how to build a strong, passive authentication layer
around iptables with fwknop.
Concrete examples illustrate concepts such as firewall log analysis
and policies, passive network authentication and authorization,
exploit packet traces, Snort ruleset emulation, and more with
- Application layer attack detection with the iptables string match
extension and fwsnort
- Building an iptables ruleset that emulates a Snort ruleset
- Port knocking vs. Single Packet Authorization (SPA)
- Tools for visualizing iptables log
- Passive OS fingerprinting with iptables Perl and C code snippets
offer practical examples that will help you to maximize your
deployment of Linux firewalls.
If you're responsible for keeping a network secure, you'll
find Linux Firewalls invaluable in your attempt to understand
attacks and use iptables - along with psad and fwsnort - to detect
and even prevent compromises.
Michael Rash is a Security Architect on the Dragon Intrusion Detection System with Enterasys Networks, Inc., and is a frequent contributor to open source projects. As the creator of psad, fwknop, and fwsnort, Rash is an expert on firewalls, IDSs, OS fingerprinting, and the Snort rules language. He is co-author of the book Snort 2.1 Intrusion Detection, lead-author and technical editor of the book Intrusion Prevention and Active Response, and has written security articles for Linux Journal, SysAdmin, and;login: .