TrinityOS is a step-by-step, example-driven HOWTO on building a very functional Linux box with strong security in mind. TrinityOS is well known for its strong packet firewall ruleset, Chrooted and Split DNS (v9 and v8), secured Sendmail (8.x), Linux PPTP, Serial consoles and Reverse TELNET, DHCPd, SSHd, UPSes, system performance tuning, the automated TrinityOS-Security implementation scripts, and much more.
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.
Spinner is useful for keeping telnet and ssh links from dropping due to inactivity. Many firewalls and some ISPs drop connections when they are perceived as idle. By having spinner running, the server is constantly sent a tiny amount of data over the link, preserving the connection. Spinner thus acts as a keep-alive. It displays a little "spinning" ASCII character in the top left corner of your terminal. It supports any terminal capable of handling VT100-style escape codes. Spinner can also function transparently by only sending null characters to the terminal. In this mode Spinner supports any terminal. It also has a mode called "Ghost in the Machine" in which you can use Spinner to write the spinner character to any TTY, not just your own.
redWall is a bootable CD-ROM firewall which focuses on Web-based reporting of the firewall's status. It includes Snort, snortsam, dansguardian, and support for fwbuilder, squidguard, reporting (using BASE/sarg/ntop/webfwlog), VPN (Openswan/PoPToP/Openvpn), Spam Filtering (spamassassin, dcc, razor2, clamav, amavis-new, dspam and maia mailguard), and mail-based, alerting. Configuration data are stored on a floppy or USB disk.
Tunix is a set of tools used to generate small bootable Linux images. It can be used to learn how to roll your own distribution, or to port embedded systems. The basic release uses busybox and has a kernel with netfilter-enabled modules. A uclibc iptables binary is included, so you can roll your small firewall from a floppy.
Telconi Terminal is an unique network management application with interactive full-screen configuration editing, browsing, help facility support, debugging, and more. It focuses on common Cisco IOS functionality present with any hardware or software configuration, and complements the command line interface with a rich set of features. It is intended for users with knowledge of Cisco IOS, and is designed to work with any IOS-based device, such as routers and switches.
Enhanced Reverse Pimpage is an enhanced version of the original rpimp by Matt Miller. Reverse Pimpage was designed to allow you to access a computer that is behind a firewall from outside that firewall itself. The way it accomplishes this is by having the client (the computer behind the firewall) send a SYN request to a certain port at certain intervals. The computer that will access the client must run the server program, and when the time interval is up it will connect. Once it's connected, the client telnets to itself and routes data back and forth between the two.