Approximately 7.6 million current accounts and 65.4 million previous accounts are affected.
Information on about 73 million current and former AT&T customers was recently posted to the dark web in a data breach, the carrier confirmed Saturday.
“AT&T has determined that a dataset published on the dark web approximately two weeks ago contained fields unique to AT&T data,” the Dallas-based company said in a statement.
AT&T said the affected data sets appear to date back to 2019 and earlier, impacting approximately 7.6 million current customers and approximately 65.4 million former account holders.
AT&T said the data set included personal information such as Social Security numbers. The company said it was unclear whether the data originated from AT&T or its vendor.
“AT&T has launched a robust investigation supported by internal and external cybersecurity experts,” the company said in a statement.
In a note to customers, the company said “a large number” of AT&T passcodes had been compromised and that it had reset the passcodes of all affected current customers.
“Additionally, we plan to contact current and former account holders whose sensitive personal information was compromised,” the company said.
AT&T said the compromised data does not appear to include personal financial information or call history.
TechCrunch reported Monday that it notified AT&T that the leaked data included encrypted passcodes that were easy to crack.
This isn't the first time the company has faced problems this year. In February, power outages temporarily disrupted cell phone service for tens of thousands of customers in the United States. The network outage was caused by a software update, the company said at the time.