AT&T is investigating a significant data breach affecting roughly 73 million people, including both current and former customers.

Exposed personal information potentially includes Social Security numbers, phone numbers, email addresses, names, birth dates, and mailing addresses.

The breach dates back to 2019 or earlier, involving data from 7.6 million active customers and 65.4 million past customers.

Uncertainty exists whether the breach originated within AT&T's systems or a third-party supplier, with no evidence of unauthorized system access found by the company.

AT&T has reset passcodes for the 7.6 million current users affected and is contacting those impacted to offer credit monitoring and advise on setting up fraud alerts.

The company is collaborating with cybersecurity experts to manage the situation, which follows a separate February outage caused by technical issues, not cyber threats.