Although AT&T has stated that it does not have evidence of unauthorized access to its systems resulting in the exfiltration of the data set, the company has not yet confirmed whether the data originated from AT&T itself or one of its vendors. The leaked data includes a wide range of sensitive customer information, such as names, home addresses, phone numbers, dates of birth, and Social Security numbers, in addition to the encrypted account passcodes.

Sam “Chick3nman” Croley, the security researcher who examined the leaked data, discovered that the encrypted passcodes could be reverse-engineered by correlating them with surrounding account data, such as customer dates of birth, house numbers, and partial Social Security numbers. This revelation prompted AT&T to take immediate action to protect its customers’ accounts.

As a precautionary measure, AT&T will be contacting all 7.6 million existing customers whose passcodes have been reset, as well as current and former customers whose personal information was compromised in the leak. The company has also provided guidance to customers on how to keep their accounts secure in the aftermath of this incident.