Reference

http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/custom-guide/s1-basic-firewall-gnomelokkit.html Red Hat's guide to basic firewall configuration. Newer documentation will appear at http://fedora.redhat.com/.

http://www.insecure.org/nmap/ This site contains information on Nmap.

http://www.securityfocus.com/ The Security Focus website.

http://www.tripwire.org/ Information and download links for the open-source version of Tripwire.