Openwall GNU/*/Linux - description from Softdepia.com:
Openwall GNU/*/Linux (Owl) is a security-enhanced operating system with Linux and GNU software as its core, compatible with other major distributions of GNU/*/Linux. It is intended as a server platform.
For more information on Owl, please refer to its homepage at:
http://www.openwall.com/Owl/ In particular, please be aware that currently the installation procedure requires Linux system administration experience. If you're used to specifying a custom Linux kernel configuration for each box then Owl is just for you!
Owl is free software, both in the sense of freedom (http://www.gnu.org/philosophy/free-sw.html) and price.
You are, however, encouraged to buy Owl on CD which saves you the download time and supports the project.
You may also order remote installation of Owl (you just boot off the CD, we do the rest), commercial support and/or donate money to support future work on Owl and related community activities.
Openwall GNU/*/Linux is a "Free to try" program. You can download and try it for an evaluation period.