XOTcl provides a highly flexible, reflective, component-based object oriented environment that integrates language support for high level object oriented concepts (which are not found in other languages) with reasonable performance. XOTcl is an extension of TCL and was derived from the impressive OTcl language developed by D. Wetherall and C. Lindblad at MIT in 1995 and extended in various ways. XOTcl's language constructs explicitly aim at the complexity in a component gluing layer that is not solved by traditional object orientation in the style of C++ or Java.
rc.firewall is configurable for dialup and static IP addresses. It is based on Linux-kernel 2.4.x, and it generates it's own configuration file. It supports specific port filtering for the internet- , intranet-, and a dmz-zone. For the DMZ-Zone, there is also a machine-specific port filtering, and redirection of specific ports of the internet-interface available. Note: Do not install this in productive environments, until you have checked the rules/tables with your own eyes.
YpFw is a frontend to ipfw and dummynet. It was developed to ease the setting and managing of ipfw rules and dummynet pipes on FreeBSD. It features a curses text interface, which allows the user to add/delete rules, update/clear rules counters, and add/delete/configure pipes. It is not meant as a replacement to ipfw; the user will need to understand ipfw and dummynet rules and syntax.
Amber sits in the tcpserver chain for qmail and implements an "amber list" for incoming mail. This neither accepts nor rejects connections, but implements a number of timing-related tricks to fake out spam and virus software that doesn't implement SMTP correctly. For example, it can defer requests from new IP addresses for a few minutes before it starts passing connections on to smtpd, pause and check for programs that send data before the HELO, and otherwise make things rough for bandit bulk mailers.