Wanting to start working with network security.?

Hello everyone! I am a really into computers. I'm 17 and computer program, however lately I have been wanting to get into network security and running network diagnostics. I have recently found a work on my network (fixed it of course) However, I want to get into network diagnostics and running security tests on my network. I know a few OS's such as the linux kernel Backtrack and Leolinux. However, I have heard the backtrack distros have some very powerful tools that a novice could do harm with. Does anyone no any network security tools I could play around with to start getting some experience with yzing my network for backdoors and hacks?