Best known for 2010 demo of technique forcing ATMs to spit out cash.
Well-known hacker Barnaby Jack has died in San Francisco, a week before he was due to show off techniques for attacking implanted heart devices that he said could kill a man from 30 feet away.
The San Francisco Medical Examiner's office said he died in the city on Thursday. It gave no details.
Jack, a security expert, became one of the most famous hackers on the planet after a 2010 demonstration in which he forced ATMs to spit out cash, dubbed "Jackpotting."
The hacking community expressed shock as the news of his death spread via Twitter early on Friday. Jack was due to appear at the Black Hat hacking convention in San Francisco next week, demonstrating how he could attack heart devices.
"Wow ... Speechless," Tweeted mobile phone hacker Tyler Shields.
Jack's most recent employer, the cyber security consulting firm IOActive Inc, said in a Tweet: "Lost but never forgotten our beloved pirate, Barnaby Jack has passed."
Jack had served as IOActive's director of embedded device security.
Jack's genius was finding bugs in the tiny computers that are embedded in equipment such as medical devices and banking machines. He received standing ovations at hacking conventions for his creativity and showmanship.
"You grimy bastard. I was just talking up about your awesome work last night," Tweeted Dino Dai Zovi, a hacker known for his skill at finding bugs in Apple products. "You'll be missed, bro."
Friends and fans alike Tweeted memorials to Jack's Twitter handle, @barnaby_jack.
Dan Kaminsky, an expert in Internet security, Tweeted that he had hoped the news of Jack's death was a prank: "God, the stories. Nobody caused such hilarious trouble like @barnaby_jack."