Results are presented from a survey of 21 persons who posted messages on 'pirate' bulletin boards in New York and California to determine their demographics and involvement in computer crime. Most of the respondents were in high school, and their primary computer offenses were piracy and phreaking. Piracy is the making of unauthorized copies of copyrighted computer programs, and phreaking is the avoiding of charges for long distance phone calls. These two types of computer crime are explained. Among the basic security rules presented for countering unauthorized computer access are the elimination of temptation, restricted knowledge of the physical location of the computer, use of a two-tier entry system, and restricted technical knowledge of the computer system. The book explains how offenders defeat these various security measures. After explaining how 'hackers' access corporate data networks such as Telenet and Tymnet, the discussion focuses on how computer criminals use electronic bulletin boards to share information on how to commit computer crime. The appendixes provide information from one underground computer bulletin board to illustrate the kind of information that circulates in the computer underground. 5 book and magazine resources.