Red Hat Linux Firewalls, by Bill
McCarty; Red Hat Press — a comprehensive reference to
building network and server firewalls using open source packet
filtering technology such as Netfilter and
iptables. It includes such topics as analyzing
firewall logs, developing firewall rules, and customizing your
firewall with graphical tools such as lokkit.
Linux Firewalls, by Robert Ziegler; New
Riders Press — contains a wealth of information on building
firewalls using both 2.2 kernel ipchains as well
as Netfilter and iptables. Additional security
topics such as remote access issues and intrusion detection systems
are also covered.