Mail2sh makes it possible to carry out shell commands by email. Email is sent to a particular user on your host and the commands will be carried out if the user and password given matches ones in /etc/passwd. Commands are executed with the user's privileges, and combined with a PGP module ensures a certain level of security for use. Note that the system is not natively encrypted, so use of an encryption mechanism is highly recommended for security reasons.
Firewall Builder consists of a GUI and set of policy compilers for various firewall platforms. It helps users maintain a database of objects and allows policy editing using simple drag-and-drop operations. The GUI and policy compilers are completely independent, which provides for a consistent abstract model and the same GUI for different firewall platforms. It currently supports iptables, ipfilter, ipfw, OpenBSD pf, Cisco PIX and FWSM, and Cisco routers access lists.
Service Guardian aims to protect servers against various things such as resource exhaustion and connection floods. It can measure the number of connections to servers' ports and, after a grace time period, compares and sees if the host is still in violation of the specified settings. If a host is in violation of the settings, it will be filtered out and dropped via netfilter/iptables.
Gargoyle is an interface for small, widely available routers such as the Linksys WRT54G series and the La Fonera. It provides functionality above and beyond what the default software provides including sophisticated dynamic DNS, quality of service, and bandwidth monitoring tools. The primary goal is to provide a polished interface for these advanced tools that is at least as easy to configure as any existing firmware. This project is based on top of OpenWrt, but unlike other Web interfaces for OpenWrt it places a strong focus an usability and is meant for average users, not just power users.
LFT (Layer Four Traceroute) is a sort of "traceroute" that often works much faster than the commonly-used Van Jacobson method and goes through many configurations of packet-filter based firewalls. More importantly, LFT implements numerous other features, including TCP, UDP, or ICMP-based traces, AS number lookups through several reliable sources, loose source routing, netblock name lookups, and more. LFT also distinguishes between layer-4 protocols, which make its statistics slightly more realistic, and gives a savvy user the ability to trace protocol routes, not just layer-3 hops.
Sshguard monitors services through their logging activity. It reacts to messages about dangerous activity by blocking the source address with the local firewall. Sshguard employs a clever parser that can transparently recognize several logging formats at once (syslog, syslog-ng, metalog, multilog, raw messages), and detects attacks for many services out of the box, including SSH, several ftpds, and dovecot. It can operate all the major firewalling systems, and features support for IPv6, whitelisting, suspension, and log message authentication.
DAXFi is a Python script that helps configure several different kinds of firewalls in a consistent way. It can run as daemon to adapt its behavior to external conditions; rules can be described with XML files, XML strings, or generated directly by the code; the program can be configured and extended with a sort of plug-ins written in Python. It comes with a Python package, useful to build other applications aimed to manipulate different firewalls in a uniform way (some example programs are included).