How To Use SpamAssassin on Win32
SpamAssassin is a wonderful open source product that performs heuristic spam analysis and RBL lookups, among other tests, to allow you to block most spam mail.
In its default form, it is designed and written for Unix platforms. This document provides information on how to get SpamAssassin working on Win32.

NTIDA
NTIDA (NT Intrusion Detection Audit) is a scripted framework dependant on thirdparty freeware utilities intended to assist administrators in easily auditing their critical NT/2K systems.

Windows NT/2000/XP Hardening
This paper is a brief security note to advise users of Windows NT, 2000 and XP workstations on how to apply patches and configure their systems to better protect them from compromise. This is emphatically not a comprehensive guide to Windows security but it is a first step in that direction.

Open Source Computer Forensics Manual
An open-source manual for computer forensics covering methodology, process and delving into technical standard operating procedures.

Easy Encryption
Fred Langa looks at the universe of products that help you protect sensitive files and data from prying eyes and hackers.

Argus
Welcome to the Argus Open Project, home of Argus, the network Audit
Record Generation and Utilization System. The Argus Open Project is
focused on developing network activity audit strategies that can do real
work for the network architect, administrator and network user.

Cisco Disovery Protocol
cdpr is used to decode a Cisco Disovery Protocol (CDP) packet, by default it will report the device ID, the IP Address (of the device), and the port number that the machine is connected to. Optionally it will decode the entire CDP packet.