Bastille Linux  
   Attempts to "harden" (tighten the configuration of) a Red Hat or Mandrake Linux installation.
   http://www.bastille-linux.org/

Linux Security  
   Linux Security, server hardening, 1U server, 24x7 server admin, monitoring, IDS, NDS, firewalls
   http://www.Linux-Sec.net

Exploit World - Linux Section  
   Known vulnerabilities on the Linux system with detailed description.
   http://www.insecure.org/sploits_linux.html

Dranch: TrinityOS  
   Step by step, example driven, HOWTO on building a Linux box with an aim towards strong security. Also, links to resources and mailing lists.
   http://www.ecst.csuchico.edu/~dranch/LINUX/index-linux.html

Hacking Linux Exposed  
   Companion Website to Hacking Linux Exposed, Osborne/McGraw-Hill. Source code from the book, updates, and other tools to secure your Linux system.
   http://www.hackinglinuxexposed.com/

Linux Audit and Intrusion Detection  
   InterSect Alliance are the creators of the SNARE Linux C2-style Audit module, and have a consulting background in advanced audit analysis, intrusion detection systems, and forensics for Unix and other operating systems.
   http://www.intersectalliance.com/projects/Snare/index.html

Penetrator Megablaster  
   A kernel module that detects and stops overflow attacks, like Linux Buffer Overflow attack security, which aim to get an interactive access to the system.
   http://www.angelfire.com/linux/borisl/MegaBlaster.html

New Security Features in Linux 2.4  
   Selective privileges (capabilities), cryptography, random number devices.
   http://www.linuxsecurity.com/feature_stories/kernel-24-security.html

Linuxbroker - Security  
   Linuxbroker provides all types of resources you need like Linux newsgroups search engine, daily news, howtos, applications releases tracking and security alerts.
   http://security.linuxbroker.com

Sardonix.org  
   DARPA-funded community project to audit the source of all Linux applications for security vulnerabilities.
   https://www.sardonix.org/

NiftyBox Advisor  
   Open-source security tools including "Advisor" to automatically notify an admin when a security advisory affects an installed package.
   http://www.niftybox.com/

StegFS - A Steganographic File System for Linux  
   Not only does it encrypt data, it also hides it such that it cannot be proved to be there.
   http://www.mcdonald.org.uk/StegFS/

Googgun Technologies Praetor module  
   Praetor is a kernel-based "Security Enabler" for Linux that provides fine-grained access control.
   http://www.googgun.com/

The Linux Kernel Auditing Project  
   The project that aims to audit the Linux kernel for security vulnerabilities and other bugs.
   http://sourceforge.net/projects/kernel-audit/

Password Management System  
   Designed for System Administrators, to handle user logins for several computers running Linux. It works with a console interface, based on the CDK library that uses ncurses. Import data from csv files and export to text files with a free definable format.
   http://passwordms.sourceforge.net/

The Digital Underground  
   Computer and Technology articles, and a members page for the "digital underground" community with text, programs, and security information.
   http://shoktek.com/du/

SSH, the Secure Shell: The Definitive Guide  
   This is a companion website for "SSH: The Secure Shell The Definitive Guide" by Daniel Barrett and Richard Silverman (O'Reilly, 2003). It contains technical details on the SSH as well as sample book material.
   http://www.snailbook.com

LinuxSecure  
   This site on Linux and security covers firewalls (iptables), intrusion detection systems (snort), securing services, and Linux security in general. The aim is to provide information about protection, detection, and reaction with respect to attacks.
   http://www.linuxsecure.de

Virtual eXecuting Environment for Linux  
   Open Source virtual-machine-type security system for Linux servers.
   http://vxe.quercitron.com