SELinux is SEcurity Enhanced Linux, it adds a complete layer of access
controls at the kernel level that can be configured to a granular level. For
example the httpd binary can be restricted to reading and writing files in
/var/www/ and /var/log/httpd/. Currently Red Hat Inc. ships SELinux and enables
it by default on Fedora Core 4 and Enterprise 4 products.
Getting Started with SELinux Guide
Guide to Writing SELinux Policy
https://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/selinux-guide/
https://www.nsa.gov/selinux/
https://fedora.redhat.com/docs/selinux-faq/
https://selinux.sourceforge.net/
