Basic Unix Security

Has anyone got any info on Unix security - I'm after the very basics as I'm a complete beginner (OS level)

Thanks

Dutt'O

Please be more specific. File security? network security? intrusion detection? secure programming techniques? What are you interested in?

And what kind of Unix?
For example, you have to put a lot more (and different) work into securing HP-UX or Solaris than you would with OpenBSD...