LSM

Linux Security Module

LSM framework built into kernel
Available as kernel patch for 2.4 kernels
Built into late 2.5 kernels and upcoming 2.6 kernels

Allows security modules to use common hooks into security logic
Modules can be loaded at run time
Modules can be tested much easier
Less coding time needed for module developers

Stacking modules
Works when modules are built with stacking in mind