If you want information specific to your UNIX setup, search
www.securityfocus.com for information. Also, check into
packetstormsecurity.org if you want to get your hands dirty.
Read this several times:
http://uwsg.iu.edu/usail/external/re...checklist.html. Fire up your favorite FTP client, and head on over to
ftp://coast.cs.purdue.edu...
When you're ready for more links, let me know... I can go on like this all day. If you want something specific, I'll do my best to oblige.