Hyperlinked definitions and discussions of many cryptographic, mathematics, logic, statistics, and electronics terms used in cipher construction and analysis.

Security issues that face the administrator, security philosophy, examples of how to secure the system from intruders.

Describes how to obtain, install and configure the enhanced IP firewalling chains software for Linux, and how they might be used, by Paul Russell.

Teaches the basics of firewall systems and give you some detail on setting up both a filtering and proxy firewall on a Linux based PC, by Mark Grennan.

A technical FAQ for the NSA SELinux project, which covers installation and implementation issues.

Firewall HOWTO collection, ids, nids, hardening, penetration testing, auditing

Discusses the possibility that crackers might generate and distribute a massive list of encrypted passwords.

Explains how to set up secure POP connections using ssh, by Manish Singh.

A tutorial on how to setup a bridge and a firewall with Linux, by Peter Breuer.

Tutorial on using ppp over telnet to do network stuff transparently through an Internet firewall. (Francois-Rene Rideau)