Arming Linux against hackers

In addition, you can compile the kernel to run in a permissive mode. This mode allows auditing of the security configuration policies to determine the required permissions for installed user applications and system operation. You can change the permissive mode of operation to enforcement at any time without rebuilding the system.

Why should you run SELinux?
The best reason to implement SELinux is to enforce mandatory access controls to confine user programs to the least privilege required for their operation.

Other noticeable improvements include:

Access control for kernel objects and services

Final thoughts
SELinux alleviates the constant requirement to update every user and system application to prevent a system compromise. You can now apply patches and updates when convenient.

Because SELinux is still a development project, the NSA does not recommend it for use on systems that contain or protect sensitive information. However, I've run SELinux during the last year, and I've experienced no system compromises.

Test it out and judge for yourself. It's free, and it works.