A self-proclaimed hacker who held over 300 million iPhones to ransom after gaining access to their iCloud details and threatening to factory reset their iPhones has pleaded guilty to blackmailing the Cupertino-based tech giant.

Kerem Albayrak, 22, claiming to be a member of the 'Turkish Crime Family' hacking group, tried to blackmail Apple after threatening to delete hundreds of millions of Apple accounts, Forbes reported on Sunday.

Albayrak was sentenced last week to two-year suspended jail term, along with 300 hours of unpaid work and an electronic curfew for six months, at Southwark Crown Court in London.

"While iPhone users have recently been warned that they need to update to iOS 13.3 or risk getting locked out of their devices, Albayrak proposed to delete their data instead," said the report.

He threatened to factory reset more than 319 iCloud accounts, effectively holding iPhone user data to ransom, as well as "other" Apple accounts.

Apple contacted law enforcement agencies in the US and the National Crime Agency (NCA) led the investigation in the UK.

In March 2017, the National Cyber Crime Unit arrested Albayrak at his home in north London. The team also seized his digital devices, such as smartphones, computers, and hard drives.

"Hacker who tried to blackmail Apple by threatening to delete 319 million accounts has been sentenced following an NCA investigation," tweeted the NCA.

Albayrak demanded that Apple made a payment of $75,000 in crypto-currency or $100,000 worth of iTunes gift cards.

In an online post, Albayrak claimed his hacking group would "have enough power to factory reset 150 accounts per minute per script," and that they could process 17 scripts per server.

The US investigators said "there were no signs of a network compromisea.