Kevin Mitnick, Hacker Who Once Eluded Authorities, Is Dead at 59

Kevin Mitnick, a reformed hacker who was once one of the most wanted computer criminals in the United States, died on Sunday, according to a statement shared Wednesday by a cybersecurity training company he co-founded and a funeral home in Las Vegas. He was 59.

His death was confirmed by Kathy Wattman, a spokeswoman for the training company, KnowBe4.

The cause was complications from pancreatic cancer. He had been undergoing treatment at the University of Pittsburgh Medical Center following his diagnosis more than a year ago, according to the King David Memorial Chapel & Cemetery in Las Vegas.

After serving prison time for breaking into and tampering with corporate computer networks, he was released in 2000 and began a new career as a security consultant, writer and public speaker.

Mr. Mitnick was best known for the crime spree during the 1990s that involved the theft of thousands of data files and credit card numbers from computers across the country. He used his skills to work his way into the nation’s phone and cell networks, vandalizing government, corporate and university computer systems.

Investigators at the time named him the “most wanted” computer hacker in the world.

In 1995, after a more than two-year-long manhunt, Mr. Mitnick was captured by the F.B.I. and charged with the illegal use of a telephone access device and computer fraud. “He allegedly had access to corporate trade secrets worth millions of dollars. He was a very big threat,” Kent Walker, a former assistant U.S. attorney in San Francisco, said at the time.

In 1998, while Mr. Mitnick awaited sentencing, a group of supporters commandeered The New York Times website for several hours, forcing it to shut down.

The next year, Mr. Mitnick pleaded guilty to computer and wire fraud as part of an agreement with prosecutors and was sentenced to 46 months in prison. He was also prohibited from using a computer or cellphone without the permission of his probation officer for the three years following his release.

Mr. Mitnick grew up in Los Angeles as an only child of divorced parents. He moved frequently and was something of a loner, studying magic tricks, according to his 2011 memoir, “Ghost in the Wires.”

By the age of 12, Mr. Mitnick had figured out how to freely ride the bus using a $15 punch card and blank tickets fished from a dumpster, and in high school he developed an obsession with the inner workings of the switches and circuits of telephone companies.

By 17, he was burrowing into different corporate computer systems and eventually had his first run-in with the authorities for those activities. It was the beginning of a decades-long cat-and-mouse game with law enforcement.

In his memoir, Mr. Mitnick disputed many of the accusations leveled against him, including that he had hacked into government computer systems.

Mr. Mitnick also claimed that he ignored the credit card numbers he gleaned in his pursuit of code. “Anyone who loves to play chess knows that it’s enough to defeat your opponent. You don’t have to loot his kingdom or seize his assets to make it worthwhile,” he wrote in his book.

Survivors include Mr. Mitnick’s wife, Kimberley Mitnick, who is pregnant with their first child, according to an obituary published by the funeral home.

A complete obituary will be forthcoming.