Some Pointers for A new Net. Admin

:confused:
Hello, Here is my situation, I'm about to graduate with an AA in Computer Science. I have learned NetWare, Linux, Unix, Windows 2000 Professional, and 2000 Server. We routinley set up "networks" in the classroom. However, being in a controlled environment, our networks are never exposed to hackers or break ins to our network. I know that keeping a network secure is one of the constant headaches of a network administrator. And before entering the work force, I feel I need to educate myself a little more than what I have already learned. They obviously don't teach us how to "hack" or to break into networks, and that is not what I am asking how to do. I understand some of the percautions needed to take, i.e. dismounting volumes, changing file permissions, but not much more than that. I have read some posts here about, and it seems a lot of people suggest to learn a programming language. So what I am getting at here is, I'm looking for some good links, or even a good book would do, to learn about common network break-ins and how to prevent them.
Thanks Again

A guide to ethical hacking -- ankit fadia

http://www.ankitfadia.com/

Check it out