Skeptic,

I recall surfing the NSA site some years back. They had quite a touching memorial page for the USS Liberty. I had only vaguely remembered it (back in Johnson's days I think). A lot of casualties. They were just in the wrong place at the wrong time.

As for Schneier's book, it is a pretty good intro book, especially for engineers. He also has a nice security company called Counterpane and publishes a worthwhile newsletter. There is a free classic text on the web. I think it's called "The Handbook of Cryptology" with downloadable pdf files for each chapter. Highly recommended. I found it helpful for a project I was involved in a while back.

Dorothy Denning has done some great work on system vulnerabilities and puts a lot of the social-technical  issues into context.

-Marty