An Architectural Overview of UNIX Network Security: A document from the Center for Information Technology, National Institutes of Health.
BlogFish: Weblog by Jonathan Weiss about Unix, BSD, security, Programming in Ruby, Ruby on Rails and Agile Development.
Computer Security: How to secure your Unix computer system (emphasis on HP-UX).
OpenBSD release errata: the OpenBSD CD errata page
Secure your Digital UNIX (Tru64) Alpha: Notes for securing a DEC/Compaq Alpha running Tru64 UNIX.
SysAdmin & Security Resource Center: Security, networking and UNIX resources for system administrators.
The Website of Johnny: About Linux/Unix, security, encryption.
Unix and Security Services and Solutions: Providing administration, installation, integration and consulting services for Unix and Security products and solutions.
Unix System Security Tools: An introduction to Unix security tools, including Ten General Security Rules.
Vapid Labs: Security, Linux, FreeBSD, IRIX, midikeys, exploit, Vulnerability, Networking