AT&T: Data breach affects 73 million or 51 million customers. No, we won’t explain.

AT&T is notifying millions of current or former customers that their account data has been compromised and published last month on the dark web. Just how many millions, the company isn't saying.

In a mandatory filing with the Maine Attorney General’s office, the telecommunications company said 51.2 million account holders were affected. On its corporate website, AT&T put the number at 73 million. In either event, compromised data included one or more of the following: full names, email addresses, mailing addresses, phone numbers, social security numbers, dates of birth, AT&T account numbers, and AT&T passcodes. Personal financial information and call history didn’t appear to be included, AT&T said, and data appeared to be from June 2019 or earlier.

The disclosure on the AT&T site said the 73 million affected customers comprised 7.6 million current customers and 65.4 million former customers. The notification said AT&T has reset the account PINs of all current customers and is notifying current and former customers by mail. AT&T representatives haven’t explained why the letter filed with the Maine AG lists 51.2 million affected and the disclosure on its site lists 73 million.

According to a March 30 article published by TechCrunch, a security researcher said the passcodes were stored in an encrypted format that could easily be decrypted. Bleeping Computer reported in 2021 that more than 70 million records containing AT&T customer data was put up for sale that year for $1 million. AT&T, at the time, told the news site that the amassed data didn’t belong to its customers and that the company's systems had not been breached.

Last month, after the same data reappeared online, Bleeping Computer and TechCrunch confirmed that the data belonged to AT&T customers, and the company finally acknowledged the connection. AT&T has yet to say how the information was breached or why it took more than two years from the original date of publication to confirm that it belonged to its customers.

Given the length of time the data has been available, the damage that’s likely to result from the most recent publication is likely to be minimal. That said, anyone who is or was an AT&T customer should be on the lookout for scams that attempt to capitalize on the leaked data. AT&T is offering one year of free identity theft protection.