IPFC is software and a framework to monitor multiple types of agents in a heterogeneous distributed environment. Agents can implement logging of elements as diverse as packet filters (like netfilter, pf, ipfw, IP Filter, checkpoint FW1, etc.), NIDS (Snort, arpwatch, etc.), Web servers, and other general devices (from syslog-servers to embedded devices). It features log collection for different security "agents", dynamic log correlation possibilities, and easy extensibility due to the generic database and XML message formats used.
IPFire is a Linux firewall distribution that is built from source and comes with lots of additional features. It is easy to set up and administer. It features a firewall with stateful inspection, a content filtering engine, traffic control (QoS), VPN technology, and a lot of logging.
IPTables-tutorial is a tutorial which explains how to install and set up iptables and netfilters on Linux. It takes you through a usable example file step by step, and helps you understand its basic functionality. The tutorial currently contains 6 different example scripts that may be used freely under GPL licensing terms.
The IPchains Firewalling Module, part of the RockSolid Linux Distribution, allows you to easily maintain a firewall based on ipchains with the Webmin look and feel. It has three modes: Newbie (select one of five security levels), Template (define from a table with protocols and directions what should be allowed to pass your firewall), and Expert (have the real ipchains experience by having every parameter under control by editing a script file which has all ipchains rules). Nearly all of the ipchains options are supported.
IPsec-Tools is a Linux port of the user-space tools from KAME. It includes libipsec (a library with a PF_KEY implementation), setkey (a tool for manipulating and dumping the kernel Security Policy Database and Security Association Database), and racoon (Internet Key Exchange daemon for automatically keying IPsec connections).
The IPtables Firewall Webmin Module helps you easily administrate an iptables firewall over a Web interface with the Webmin Look and Feel. It has three modes: Newbie (select between 5 predefined security levels), Template (configure on a per Interface/per Protocol base) and expert (rule iptables as a guru has to).
ROPE is an open-ended iptables match module that allows rules to be written using a simple but powerful scripting language. It is designed for controlling complex high-level protocols that cannot be blocked using traditional criteria based on port numbers (etc.). Criteria can include tests on any field of the IP, UDP, or TCP headers as well as the packet data payload.