Underground And Other Stuff

Ever wanted to become a true expert on computer security? Most agree that to do so, you need to 1) acquire knowledge from the "hacker's" point of view, and 2) stay up-to-date with the latest information. You can do both by frequenting www.packetstormsecurity.org and reading advisories, exploit code, and news. It is an excellent site to find security-related tools, such as the IDS "Snort" and the port-scanner "Nmap."
Also, try downloading GFI's LanGuard Network Scanner at www.gfi.com/lannetscan/ and scanning your own PC and others in your network. You will invariably learn something new and useful.