Dante is a free implementation of the proxy protocols SOCKS version 4 and SOCKS version 5 (RFC 1928). It can be used as a firewall between networks, controlling outgoing traffic. The package consists of two parts: a socks server and a proxy client that supports socks, HTTP proxies, and UPnP. RFC 1961 (GSSAPI) is supported in both the client and the server. Commercial support is available.
DeleGate is a multi-purpose application level gateway or proxy server that mediates communication of various protocols, applying cache and conversion for mediated data, controlling access from clients, and routing toward servers. It translates protocols between clients and servers, converting between IPv4 and IPv6, applying SSL (TLS) to arbitrary protocols, merging several servers into a single server view with aliasing and filtering. It can be used as a simple origin server for some protocols (HTTP, FTP, and NNTP).
The Falcon Project (Free Application-Level CONnection kit) is an open firewall project with the intention of developing a free, secure and OS-independent firewall system. Falcon consists of three major modules: Falcons's own proxies (written in Perl); 3rd-party proxies (squid / qmail / BIND8), each modified for chroot environment; and general concepts for OS hardening, chrooting etc.
fBuilder Plus is a Web-based utility for building and configuring your ipchains/iptables-based Linux firewall. It performs all actions in real-time and includes a Firewall Creation Wizard, edit, insert, and delete capabilities for firewall rules, rule shifting, support for DHCP clients, DMZ creation through firewall wizard, NAT capabilities, support for IP aliases, custom protocols, user defined chains, limit matches, automatic log rule creation, state checking, log reporting, email alerts, export capabilities, and an enhanced firewall log parsing utility.
fCluster is a multi-threaded client/server redundancy application for your Linux firewall solution. fCluster is designed for the production environment with features that include: dynamic firewall synchronization, support for both ipchains and netfilter, user definable polling intervals and fail-over sequence, and email notification of a system failure. It also includes a Perl administration utility that allows you to configure both the server and the client from one machine, and view the status of the local and remote machines.