Stik's Security Module
- 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).
- http://stiksecmod.sourceforge.net

Rule Set Based Access Control (RSBAC) for Linux
- 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
- http://www.rsbac.de/

Medusa DS9 Security System
- 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).
- http://medusa.fornax.sk/

Linux Security Protection System (LinSec)
- 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.
- http://www.linsec.org/

The Linux Encryption HOWTO Homepage
- The Linux Encryption-HOWTO seeks to describe all major development activities around Linux that provide encryption features to the kernel.
- http://encryptionhowto.sourceforge.net/

Security ACLs for Linux kernel
- The site provides a patch for extended attributes and access control lists for Linux kernel.
- http://acl.bestbits.at/

Security patch for Linux kernel 2.4
- 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.
- http://www.grsecurity.net/

Flask: An Operating System Security Architecture
- 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.
- http://www.cs.utah.edu/flux/fluke/html/flask.html