The author, Cliff Stoll, was an astronomer working as a computer systems manager at a government lab in Berkeley, California in the late 1980's. He discovered a 75-cent error in the accounting on one of the mainframe computers, and nobody really cared. Although his bosses encouraged him to ignore it, the error intrigued him, and he tried to figure it out. One of the advantages of graduate-student life is having time to think about such problems. He eventually discovered the hacker that had broken into his computer, but instead of blocking him out, he let him wander around and tracked his movements.
The hacker appeared to be looking for defense-related information, and attempted to break into military computers all over the country. It is amazing to read how easily he gained access to so many different systems using the default or guest password. The author tried to call people to warn them that their computers are being broken into; it is frightening how little the officers in charge of some of the military bases cared about the threat. In an effort to divert the hacker, the author invented a fake project called 'SDInet' (remember SDI?) and distracted him with emails, files, and references to classified (but nonexistent) documents.
Although the tracking was not done through dark alleyways but through networks, phone lines, and computers, the chase was nonetheless intriguing. Like a true scientist, the author adopted some very nonconventional methods in his search for truth, noting that "it's always easier to beg forgiveness than to ask permission".
By now, all of the specific security holes mentioned in the book have been fixed; however, the overall message about computer security is still relevant today. This book is a great way to learn a little bit about some of the network security issues while enjoying a good mystery story.