If you're willing to spend the money, you may want to look at the Hacking Exposed series, recently mentioned in a few threads here. Right now I think it runs at about $50 for the main book (Hacking Exposed 4th Edition). To all those quick to say he should not be doing this, how can you know you have a secure network if you have not tried to get in yourself? That is why there are _security_ tools like SAINT/SATAN out there.