The Flask operating system security architecture provides flexible support for security policies. The architecture has previously been implemented in two research operating systems, Mach and Fluke, and is now being implemented in the Linux kernel.

The Linux Security Modules (LSM) project provides a lightweight, general purpose framework for access control. The LSM framework allows access control models to be implemented as loadable kernel modules. LSM is the only Secure Linux project that has a chance of being included into a mainstream OS kernel (supposedly 2.5).

The main aim of the project is to introduce Mandatory Access Control (MAC) mechanism into Linux, based on capabilities, filesystem access domains, IP labeling lists and socket access control.

Medusa DS9 is a project to enhance the security of Linux kernel, which implements the ZP Security Framework. The main goal of a project is to implement a framework for implementation of any security model (unlike other secure Linux kernel projects).

RSBAC is another MAC kernel security enhancement project for Linux. The standard package includes a range of access control models like MAC, RC, ACL. Additionally, the runtime registration facility (REG) makes it easy to implement your own access control model as a kernel module and get it registered at runtime.

The site provides a patch for extended attributes and access control lists for Linux kernel.

Grsecurity is an extensive set of security patches to the 2.4 tree of Linux kernels. The goal of the project is to create the most secure system possible while requiring minimum configuration changes.

Stiksecmod is another loadable kernel module (LKM) to offer labeling, privileges, and auditing for Linux. The project seems to be in early stages of development (alpha code).

The Linux Encryption-HOWTO seeks to describe all major development activities around Linux that provide encryption features to the kernel.