Distributions

Astaro Internet Security
Appliance-based special-purpose hardened Linux distribution with firewall, VPN, anti-virus functionality. Some functionality is available for free for home use, the rest is commercial.
http://www.astaro.com

Devil-Linux
Small CD-based distribution used for firewalls, routers. System configuration settings are stored on separate floppy disk. Descriptions, news, documents, downloads, links.
http://www.devil-linux.org/

EnGarde
Server distribution, goal: provide level of security needed to create corporate web presence or conduct business on Web. Security achieved via included software and using principle of least privilege; available for use.
http://www.engardelinux.org/

HP Secure OS Software for Linux
Server platform using compartmentalization to contain processes to known part of filesystem and network; has system level auditing, supports remote configuration. Mostly closed source. Was commercial product, now discontinued, unsupported.
http://www.hp.com/security/products/linux/

Owl
Openwall GNU/*/Linux is a server distribution; main means to security: proactive source code review, privilege separation; several other means also used. Available for use. English, French, German, Russian.
http://www.openwall.com/Owl/

Project Plan-B
Bootable linux live CD-ROM for system and network security testing.
http://www.projectplanb.org/

Security Enhanced Linux
NSA research prototype made public, has modified kernel, several utilities; has enhanced security-related functions designed to show value of mandatory access controls and how such can be added to Linux; not a full OS distribution.
http://www.nsa.gov/selinux/

Sentry Firewall CD
Linux-based bootable CD suitable for use as low cost, easy to maintain firewall or IDS node.
http://www.sentryfirewall.com/

Migrating to Astaro Security Linux
Fed up with costly, complex firewalls, e-gaming firm eBet Ltd., picks open source security; senior systems administrator knew he needed to upgrade from Check Point 4.0 perimeter firewall. [Linux Journal] <small>(December 15, 2003)</small>
http://www.linuxjournal.com/article/7313