_I first read Clifford Stoll's book in the early 90's and was fascinated by his gripping tale of chasing an intruder through global military networks. If you are interested in cybersecurity, ethical hacking, computers, or just enjoy a great tale of espionage, this is a great book!
From Amazon's description:
"Cliff Stoll was an astronomer turned systems manager at Lawrence Berkeley Lab when a 75-cent accounting error alerted him to the presence of an unauthorized user on his system. The hacker's code name was "Hunter" -- a mystery invader hiding inside a twisting electronic labyrinth, breaking into U.S. computer systems and stealing sensitive military and security information. Stoll began a one-man hunt of his own, spying on the spy -- and plunged into an incredible international probe that finally gained the attention of top U.S. counterintelligence agents. The Cuckoo's Egg is his wild and suspenseful true story -- a year of deception, broken codes, satellites, missile bases, and the ultimate sting operation -- and how one ingenious American trapped a spy ring paid in cash and cocaine, and reporting to the KGB."