The Dallas-based telecom giant disclosed details of the breach in a press release and inan SEC filingFriday morning.
In March, the companyacknowledged a vendor breach that took place in Januaryand affected 9 million people.
But this latest breach is notable in that it affects the vast majority of its wireless customers.
The company said itplans to notify 110 million of themabout what happened andhas set up a webpage with information.
A spokesperson told TechCrunch that the investigation involves the FBI and the Department of Justice.
TheFCC saidFriday in a post on X that it is investigating the AT&T breach.
