The company said it is conducting an investigation with the help of internal and external cybersecurity experts, but has not yet determined whether the data came from AT&T or its vendor.
“At this time, AT&T has no evidence of unauthorized access to its systems that would result in the exfiltration of data sets,” the company said in a statement.
AT&T said the data appears to date back to 2019 or earlier and includes information from 7.6 million current AT&T account holders and approximately 65.4 million former account holders.
The company said it has notified customers whose data was breached and will pay credit monitoring costs where applicable.
Many well-known companies have fallen victim to data breaches, including both of AT&T's biggest rivals. Verizon has had multiple reports of data breaches over the years, and T-Mobile has had at least eight incidents since 2018, including in 2021 where hackers stole the data of millions of customers. Cases from 2007 are also included. A hack by a third-party company may have compromised American Express cardholders' account information this year.
AT&T came under scrutiny last month after a major cellphone outage affected more than 1.7 million customers and disrupted 911 service in some states. The company said it was caused by a technical error, not a cyberattack.
