I have had a few people ask me this very question recently, so i decided to post my source for information on securing boxes, and some applications...
If you have questions, ask
But yes, you guys have heard of that NSA agency thingie, right? Well, it just so happens that they write some of the most amazing and paranoid guides to securing boxes...:
Security Configuration Guides
Enjoy, most are quite a read
at least its dual core opteron with a t of storage 
