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.
grsecurity is a complete security system for Linux 2.4 and 2.6 that implements a detection/prevention/containment strategy. It prevents most forms of address space modification, confines programs via its Role-Based Access Control system, hardens syscalls, provides full-featured auditing, and implements many of the OpenBSD randomness features. It was written for performance, ease-of-use, and security. The RBAC system has an intelligent learning mode that can generate least privilege policies for the entire system with no configuration. All of grsecurity supports a feature that logs the IP of the attacker that causes an alert or audit.
snowdrop is a steganographic text document and C code watermarking tool that uses redundant, tamper-evident and modification-proof information embedded in the content itself, instead of the medium, to simplify tracking of proprietary code leaks, sensitive information disclosure, etc.
The Paketto Keiretsu is a collection of tools that use new and unusual strategies for manipulating TCP/IP networks. They tap functionality within existing infrastructure and stretch protocols beyond what they were originally intended for. It includes Scanrand, an unusually fast network service and topology discovery system, Minewt, a user space NAT/MAT router, linkcat, which presents a Ethernet link to stdio, Paratrace, which traces network paths without spawning new connections, and Phentropy, which uses OpenQVIS to render arbitrary amounts of entropy from data sources in three dimensional phase space.
Weplab is a tool to review the security of WEP encryption in wireless networks from an educational point of view. Several attacks are available, so it can measure the effectiveness and minimum requirements of each one. Currently, weplab supports several methods, and it is able to crack the WEP key from 600,000 encrypted packets.
Hardened Debian improves Debian GNU/Linux with high security and hardening features, hardened kernels and packages, DHKP, and other security related enhancements. It makes systems more difficult to compromise using common attacks such as race conditions, chroot jail escapes, and buffer overflows.