a taste of computer security   (link)

http://www.kernelthread.com/publications/security/
Given the nature and scope of the field, it would require one or more books to even briefly touch upon all that is known about computer security. This document's goal is only to give you a taste of (a subset of) the subject. The various sections are not uniform in their depth or breadth, and the document's overall structure is not pedagogical. I could have titled it Thinking Aloud On Computer Security, if not for the somewhat pompous undertone.