How to get a BitcoinShortly after, the seller mentioned being booted out of the servers but claimed to have backed up the data.

"I think they already found out because we lost access to the backdoored servers," the seller said, according to Motherboard. "It's backed up in multiple places."

A T-mobile spokesperson said the company is "aware of claims made in an underground forum" and is "actively investigating their validity."

"We do not have any additional information to share at this time," the spokesperson added.

Cryptocurrencies have been at the center of recent high-profile cyberattacks, demanded as ransom by criminals because transactions are either anonymous or very difficult to trace.

In the US, the Biden administration is said to be ramping up efforts to trace cryptocurrencies used in cyberattacks and is planning to offer bounties of up to $10 million for information that will help catch criminals.