GRSecurity is a Kernel patch, which helps protecting against common exploits like stack overruns. Please consult their website http://www.grsecurity.net for details.
It also includes an ACL system which on Devil-Linux is turned off by default.
Many parameters can be switched on or off via the configuration file /etc/sysconfig/grsecurity.proc.
The ACL system can be enabled in the file /etc/sysconfig/config, but you'll have to create and test the ACLs yourself!
You find documentation about GRSecurity in the folder /usr/share/docs/grsecurity on the Devil-Linux CD and on their website http://www.grsecurity.net.