LinuxKernel > SELinux
Security-Enhanced Linux (SELinux) is a project to implement mandatory access control under Linux. This project was initially developed by the National Security Agency (NSA), as a reference implementation.
Debian SELinux support
The Debian packaged Linux kernels have SELinux support compiled in, but disabled by default. To enable it, see the Setup Notes.
Setup - How to setup your Debian system to use SELinux
Issues - Issues currently affecting SELinux support
Notes - Scratch space with some notes about SELinux use and setup
Please note that SELinux is a Linux-specific feature and Debian packages shouldn't assume it is present (unless they're Linux-specific packages for some reason). Note for developers: Remember to check whether this is a Linux platform by using dpkg-architecture variables in debian/rules, and conditionalise the libselinux Build-Dependency using  tags. Something like [linux-any] should be fine.
There are mailing lists about SELinux support in Debian for both user support and development hosted on alioth. Use the SELinux lists overview to subscribe to the lists or browse the archives.
External Debian SELinux links
External SELinux links
Security-Enhanced Linux - Documentation - Red Hat -- this is probably the best documentation on SELinux available and almost all of it also applies to Debian.
SELinux Project Wiki -- "the official Security Enhanced Linux (SELinux) project page"