I am currently reading Counter Hack by Ed Skoudis. It is a good read, in that it takes many of todays common exploits and explains them in detail followed by the appropriate defense. He also has, though it wasn't there when I went to Borders (sob) a lecture series. (3) Which basically walks you through setting up your lab, performing the exploits and their appropriate defense. He believes as many do that only with a complete understanding of your opponents tools can you ever hope to keep them at bay. I do this for a living (like most of us do) and I don't really feel comfortable giving advice based completely on others research. I want to see for my self just how viable some of these exploits are. I guess I am fortunate enough to have the extra machines (not the extra time) to play with some of this stuff. Keep learning, but keep it legal too.