AT&T says its nationwide cellular outage was caused by a software update, not a cyberattack

• The widespread AT&T cellular outage was caused by a software update, the network said.
• The company said it was not caused by a cyber attack, despite federal agencies looking into the downtime.
• The issue left some without service for close to 12 hours on Thursday and many angry customers.

AT&T says it believes its sweeping cellular outage that left customers without service for up to 12 hours on Thursday wasn't a cyberattack.

It was a software update gone wrong, AT&T said.