Mitnick gained unauthorized access to his first computer network in 1979, at 16, when a friend gave him the phone number for the Ark, the computer system Digital Equipment Corporation (DEC) used for developing their RSTS/E operating system software. He broke into DIC's computer network and copied DEC's software, a crime he was charged with and convicted of in 1988. He was sentenced to 12 months in prison followed by three years of supervised release. Near the end of his supervised release, Mitnick hacked into Pacific Bell voice mail computers. After a warrant was issued for his arrest, Mitnick fled, becoming a fugitive for two and a half years.
According to the U.S. Department of Justice, Mitnick gained unauthorized access to dozens of computer networks while he was a fugitive. He used cloned cellular phones to hide his location and, among other things, copied valuable proprietary software from some of the country's largest cellular telephone and computer companies. Mitnick also intercepted and stole computer passwords, altered computer networks, and broke into and read private e-mail. Mitnick was apprehended in February 1995 in Raleigh, North Carolina. He was found with cloned cellular phones, more than 100 clone cellular phone codes, and multiple pieces of false identification.
After a well-publicized pursuit, the FBI arrested Mitnick on February 15, 1995, at his apartment in Raleigh, North Carolina, on federal offenses related to a 2½-year period of computer hacking.
Mitnick served five years in prison — four and a half years pre-trial and eight months in solitary confinement — because, according to Mitnick, law enforcement officials convinced a judge that he had the ability to "start a nuclear war by whistling into a pay phone". He was released on January 21, 2000. During his supervised release, which ended on January 21, 2003, he was initially forbidden to use any communications technology other than a landline telephone. Mitnick fought this decision in court, eventually winning a ruling in his favor, allowing him to access the Internet. Under the plea deal, Mitnick was also prohibited from profiting from films or books based on his criminal activity for seven years. Mitnick now runs Mitnick Security Consulting LLC, a computer security consultancy.