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.
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.
Addns.pl is a self-contained DynDNS update client for DynDNS.org (and possibly others). It supports a variety of IP detection methods including external webcheck/router pages. It also supports multiple configurations and hostnames, smart abuse prevention, and custom/static/dynamic DNS, and can run as a daemon, commandline options only, or with a configuration file.
Dual DHCP DNS Server is a DHCP server combined with a caching DNS server that is sensitive to the names that were allocated by the DHCP server. It has built in dynamic updates, and also supports BOOTP PXE network booting and client specific options. It is self-configuring, doesn't require the creation of zone files, and uses little memory and CPU time. Either one of the two services can be turned off.
OpenNetAdmin provides a database managed inventory of your IP network (IPAM). Each host can be tracked via a centralized AJAX-enabled Web interface that can help reduce tracking errors. It also has the ability to generate DHCP and DNS configuration for individual servers from the data stored in the database. There is a command line interface for batch scripting that can be accessed remotely or locally.
YaCy is a search engine that anyone can use to index the Internet (WWW and FTP) or to create a search portal for others (Internet or intranet). The scale of YaCy is limited only by the number of users. and can index billions of web pages. In P2P mode it is fully decentralized. All users of the search engine network are equal and it is not possible for anyone to censor the content of the distributed index.
SendIP is a command-line tool to send arbitrary IP packets. It has a large number of options to specify the content of every header of a RIP, RIPng, BGP, TCP, UDP, ICMP, or raw IPv4/IPv6 packet. It also allows any data to be added to the packet. Checksums can be calculated automatically, but if you wish to send out wrong checksums, that is supported too.