NARC (Netfilter Automatic Rules Configurator) is a free firewalling package for Netfilter/Iptables, released under the BSD license. It attempts to simplify the setup of a firewall (stateful packet filter) via the iptables tools. It is a bash shellscript that generates (hopefully) sensible and secure rules for Netfilter based on a simple configuration file. It features quick setup via a simple configuration file, connection tracking (and fragmentation reassembly), customized logging, probe detection (TCP & UDP), and much more.
FireHOL a simple yet powerful way to configure stateful iptables firewalls. It can be used for almost any purpose, including control of any number of internal/external/virtual interfaces, control of any combination of routed traffic, setting up DMZ routers and servers, and all kinds of NAT. It provides strong protection (flooding, spoofing, etc.), transparent caches, source MAC verification, blacklists, whitelists, and more. Its goal is to be completely abstracted and powerful but also easy to use, audit, and understand.
Snowfence is a simple no-configuration-required Linux iptables firewall for the Sharp Zaurus. It limits the ability of potential attackers to access the Zaurus's services remotely while still allowing the Zaurus's legitimate local user to make use of the network and USB cradle as usual.
IP-Array is a Linux iptables firewall script written in bash. It allows the creation of precise, stateful rules, while remaining easy to configure. IP-Array supports VPN, traffic shaping (creation of custom HTB and SFQ qdiscs, classes, and filters), multiple external interfaces, multiple LANs, multiple DMZs, NAT, logging, MAC address matching, packet marking, syslog logging, and various sysctl settings. It also includes some presets and autoconfig options for common needs like DNS, FTP, SMTP.
homeLANsecurity is a series of shell scripts for loading iptables firewall rules. The goal of these scripts is to provide an easy to manage framework for standard iptables rule sets. The scripts are well documented and are easily edited. It is primarily designed to operate on home or small office gateway Linux system, but the scripts can be easily adapted to protect an individual Linux server or workstation. homeLANsecurity's command set is written to support loading, clearing, saving, restoring, testing, and displaying of iptables rules. The configuration supports NAT, port forwarding of common services, TOS packet mangling, OpenVPN, Squid transparent proxy, IP address banning, adaptive banning, and connection tuning. Custom iptables rules are easily inserted without any editing of the scripts themselves.
Lokiwall is a firewall script for Linux. In addition to the standard function of easily limiting network traffic, it features dual routing (using two Internet connections simultaniously), connection fail-over, load balancing, traffic control, advanced masquerading, advanced DNAT, and advanced marking (to direct specific traffic to a certain interface). The advanced features require some kernel patches. The standard features will work on a default Linux system with iptables and iproute2.