Hackers know things that you don't. That's their edge. It's the reason that they are able to break into networks, leaving a path of destruction in their wake. This book discusses some of the tricks of the hacker trade -- things that are well known in the hacker community but all too foreign to the I/T support staff. The intention is to dispel some of the common myths and misconceptions surrounding computer network security which lead to vulnerabilities that hackers can exploit. Techniques and tools for defending against such attacks are also discussed.