FreeBSD was one of the first widely deployed free operating systems to provide mandatory access control. It supports a number of classic MAC models. This tutorial paper addresses exploiting this implementation to enforce typical enterprise security policies of varying complexities.
Cite
@article{arxiv.0706.1755,
title = {FreeBSD Mandatory Access Control Usage for Implementing Enterprise Security Policies},
author = {Kirill Bolshakov and Elena Reshetova},
journal= {arXiv preprint arXiv:0706.1755},
year = {2007}
}