He rose to fame after showing how to make cash machines spit out cash – a technique known as Jackpotting.
An experienced hacker who planned to reveal details of how heart implants can be hacked has died unexpectedly in San Francisco.
The city’s medical examiner’s office announced that Jack Barnaby Jack died on Thursday, but did not give more details.
Jack, who first made a name for himself in 2010 when he demonstrated how to hack a cash machine, was set to describe medical device vulnerabilities at the Black Hat security conference in Las Vegas next week.
One technique, he said, could kill a man from 30ft away. IOActive, the security firm at which Mr Jack was director of embedded devices, said it was preparing a statement.
The company tweeted: "Lost but never forgotten our beloved pirate, Barnaby Jack has passed."