Documentation

Firewall Piercing mini-HOWTO
Tutorial on using ppp over telnet to do network stuff transparently through an Internet firewall. (François-René Rideau)
http://en.tldp.org/HOWTO/Firewall-Piercing/

Firewalling and Proxy Server HOWTO
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.
http://en.tldp.org/HOWTO/Firewall-HOWTO.html

Installing a firewall, Part 1
Get the details of a secure Trustix 1.1 installation
http://www.itworld.com/Sec/2211/LWD111010fwinstall1/

Introduction to Linux Networking and Security
Brief introduction to the IP networking services, how to configure them, and how to set up a relatively secure Linux workstation. Published in ACM Crossroads, the ACM student magazine.
http://www.acm.org/crossroads/xrds6-1/linuxsec.html

Linux Bridge+Firewall Mini-HOWTO
A tutorial on how to setup a bridge and a firewall with Linux, by Peter Breuer.
http://en.tldp.org/HOWTO/Bridge+Firewall.html

Linux Firewall Howto
Firewall HOWTO collection, ids, nids, hardening, penetration testing, auditing
http://www.linux-sec.net/

Linux IPCHAINS-HOWTO
Describes how to obtain, install and configure the enhanced IP firewalling chains software for Linux, and how they might be used, by Paul Russell.
http://en.tldp.org/HOWTO/IPCHAINS-HOWTO.html

Linux Security HOWTO
Security issues that face the administrator, security philosophy, examples of how to secure the system from intruders.
http://en.tldp.org/HOWTO/Security-HOWTO/

Linux Security HOWTO
General overview of security issues that face the administrator of Linux systems. It covers general security philosophy and a number of specific examples of how to better secure your Linux system from intruders.
http://scrye.com/~kevin/lsh/t1.html

Linuxs security basics
How to achieve the goal of every system admin: boring, predictable computers
http://www.itworld.com/Man/3872/lw-01-security/

Network Security Information: UNIX
Network Security Library has links to many UNIX (and, especially, Linux) security articles on host hardening, security admin guides, and special purpose hardening tips.
http://www.windowsecurity.com/whitepapers/unix_security/

Ritter's Crypto Glossary and Dictionary of Technical Cryptography
Hyperlinked definitions and discussions of many cryptographic, mathematics, logic, statistics, and electronics terms used in cipher construction and analysis.
http://www.ciphersbyritter.com/GLOSSARY.HTM

Rusty's Remarkably Unreliable Guides
Netfilter project provides HOWTOs for packet filtering, NAT and netfilter code hacking for Linux.
http://people.netfilter.org/~rusty/unreliable-guides/

Secure POP via SSH mini-HOWTO
Explains how to set up secure POP connections using ssh, by Manish Singh.
http://en.tldp.org/HOWTO/Secure-POP+SSH.html

Securing NIS
Provides a checklist on how to secure UNIX/Linux NIS (formerly YP) services in an intranet environment.
http://www.eng.auburn.edu/users/doug/nis.html

Setting up a secure Linux server
Setting up a secure Linux server using RedHat and the Linux From Scratch system.
http://www.fiveanddime.net/ss/secureserver.html

A Short History of Cryptography
A brief historical analysis of the management of cryptography.
http://www.all.net/books/ip/Chap2-1.html

A Simple Scheme to Make Passwords Based on One-Way Functions Much Harder to Crack
Discusses the possibility that crackers might generate and distribute a massive list of encrypted passwords.
ftp://ftp.cs.arizona.edu/reports/1994/TR94-34.ps

UnOfficial SELinux FAQ
A technical FAQ for the NSA SELinux project, which covers installation and implementation issues.
http://www.crypt.gen.nz/selinux/faq.html

YoLinux: Internet Server Security HowTo and Tutorial
This tutorial covers the installation and use of hacker protection software such as Portsentry, tripwire, ssh. It also covers configuration and administration steps to make a Linux server secure against hackers.
http://yolinux.com/TUTORIALS/LinuxTutorialInternetSecurity.html