This book shows you how to secure your network from top to bottom without spending a penny on security software using best of breed open source software including Snort, Nessus, and Ethereal. This book is a comprehensive step-by-step guide to securing your network using freely available software. It discusses the pros and cons of using some of the free software and also demonstrate the installation, configuration, and use of the software to secure your network. It is intended as a one-stop manual for network security for those on a budget, or those simply wanting to increase their network knowledge. This book covers all aspects of securing your network. It discusses the business case for using open source and free software security solutions. It also touches upon the various free options to cover a given security concern, and then walk through an actual implementation using the best of breed product, providing actual real-world examples.