Security Strategies in Linux Platforms and Applications, 3rd Edition

Firewalls and Mandatory Access Controls in a Layered Defense

A firewall may be a common first line of defense when it comes to remotely accessing a system, but it shouldn’t be the last. In addition to the firewall, a system administrator may implement TCP Wrappers and mandatory access controls using either AppArmor or SELinux. Mandatory access controls are permissions that have been set administratively. Individual users cannot change them.

When it comes to protecting your remote services, however, the starting point should be a firewall. Linux has made several attempts to implement a firewall. The initial implementation, ipfwadm, based on BSD’s ipf, was included with Linux 2.0. When Linux 2.2 was released, it included ipchains. That was replaced ...