T-Mobile has confirmed it has suffered a data breach, but has offered no details as to how many of its customers have been impacted, nor what information may have been compromised.

A Sunday (Aug. 15) message on an underground forum, according to DigitalTrends, came from someone claiming to possess personal data belonging to 100 million people. The message didn’t mention T-Mobile, but the seller told Motherboard the data belonged to “T-Mobile USA” customers and contains everything including names, Social Security numbers, phone numbers, home addresses, driver license information and other data.

Motherboard said it was able to confirm the accuracy of the stolen data after reviewing a sample.

“We are aware of claims made in an underground forum and have been actively investigating their validity,” a T-Mobile spokesperson said, according to The Boston Globe. “We do not have any additional information to share at this time.”

The thief, according to Tom’s Guide, posted a For Sale sign on an online cybercriminal forum and is asking for about $284,000, or about 6 bitcoin, for the information.