What caused AT&T’s massive cellular network outage?

The AT&T phone service outage affected thousands of users across the United States, raising concerns among the public and officials that the nation’s largest cell phone service provider had become the victim of a cyberattack.

The outage, which began around 3:30 a.m. ET on Thursday, reached nearly 73,000 reported incidents by noon and was fully resolved by 3 p.m., according to outage tracker DownDetector.

The outage that deprived thousands of users across the United States of cell phone service since Thursday morning was attributed to a coding error by AT&T without providing further details.

“Based on our initial review, we believe today’s outage was caused by the application and execution of an incorrect process as we were expanding our network, and not by a cyberattack,” the Dallas-based company said.

The ten cities hardest hit by AT&T, where more than 58,000 power outages were reported around noon ET on Thursday, were: Houston, Chicago, Dallas, San Antonio, New York, Atlanta, Austin, Miami, Indianapolis and Charlotte.

As of 9 p.m., there were fewer than 1,000 reports of AT&T network outages.

AT&T-owned Cricket Wireless had more than 9,000 outages at one time, but reports also decreased in the afternoon.

Users of other carriers like Verizon and T-Mobile also reported problems, but those companies said their networks were operating normally and that the problems were likely reported by customers trying to connect to AT&T users. Went.

During the outage, some iPhone users saw emergency messages in the status bar of their cell phones. The message indicates that the device is having trouble connecting to your cellular provider’s network, but according to Apple Support, it can make emergency calls on other carrier networks.

AT&T also said that its owned FirstNet network, which provides cellular coverage for first responders, including police and fire departments, remained operational during the outage.

AT&T users also did not lose the ability to make calls, send text messages, and browse the Internet over Wi-Fi, although they could only connect to lines not affected by the blackout or to other phones connected to the Wi-Fi network.

The decline in cellular service at AT&T, the largest operator in the country with more than 240 million customers, has raised concerns among officials.

National Security Council spokesman John Kirby said the Federal Communications Commission contacted AT&T about the outage and the Department of Homeland Security and the FBI are also investigating the matter.

Kirby said Thursday afternoon: “We’re working very hard to see if we can get to the truth about what really happened.”

The FBI acknowledged that it had been in contact with AT&T, warning that if they found evidence of any type of malicious activity, they would “respond accordingly.”

The blackout also raised concerns on Capitol Hill.

“We are working to evaluate today’s disruption to fully understand what went wrong and what we can do to prevent similar incidents from happening in the future,” said Republican Cathy McMorris Rodgers of Washington in a statement. can be done.” Who presides over the House. Energy and Commerce Committee, and Ohio Republican Bob Latta, chairman of the Communications and Technology Subcommittee.

Around noon ET Thursday, AT&T announced it had taken “immediate action” to restore about three-quarters of the network.

Later, at approximately 3 p.m., approximately 12 hours after the outage began, AT&T announced full restoration of service to affected customers.

“We sincerely apologize,” AT&T told its customers in a statement. “Keeping our customers engaged is our top priority and we are taking steps to ensure our customers do not have a similar experience again in the future.”

AT&T could face fines for disconnecting affected customers from 911 emergency service, according to industry analysts cited by CNN.

With information from the Associated Press.