System administrators need to stay ahead of new security vulnerabilities that leave their networks exposed every day. A firewall and an intrusion detecting 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 kernl, and it exaplins how they provide strong filtering, Network Address Translation (NAT), state tracking and application layer inspection capabilities that rival may commercial tools. You will learn how to deploy iptables as an IDS with psad and fwsnort and how to build a strong, passive authentication layer around iptable...