The security researcher who hacked into a moving Jeep earlier this year has resigned as an engineer at Twitter Inc after three years on the job, a person familiar with the matter said.
Charlie Miller, a former National Security Agency hacker who is the one of the world's best-known security experts, declined to comment on his departure or say what he would do next.
A Twitter spokesman could not immediately be reached for comment.
Miller's latest feat, breaking into a moving Jeep as it drove on the highway, was done with IOActive researcher Chris Valasek and was the subject of talks at this month's security conferences in Las Vegas.
Their efforts, which were coordinated with manufacturer Fiat Chrysler Automobiles NV, prompted the first vehicle recall to protect drivers from possible malicious hacking.
FCA USA LLC recalled 1.4 million vehicles to install software intended to prevent hackers from emulating the experiment, which used the cellular network to enter the entertainment system and then win control of the engine, brakes and steering.
Shares in Twitter, which is seeking a permanent chief executive officer, have fallen by more than 40 percent from the first day of trading in 2013 level and set a record low as the broader market sank on Monday.