AT&T probes sudden outage as cybersecurity concerns rise

WASHINGTON (TND) — AT&T customers were left experiencing outages Thursday morning prompting an investigation into a possible cyberattack.

Sources told ABC News that the FBI and Department of Homeland Security (DHS) are now urgently investigating to determine whether or not the outages were a result of a cyberattack or hack.

A confidential memo obtained by ABC News explains that "the cause of the outage is unknown and there are no indications of malicious activity," according to U.S. Cybersecurity and Infrastructure Security Agency (CISA).

However, AT&T reported the outage was the result of a technical error, not a malicious attack.

"Based on our initial review, we believe that today’s outage was caused by the application and execution of an incorrect process used as we were expanding our network, not a cyber attack,” the company said.

AT&T customers reported having issues making and receiving calls or texts, according to Downdetector.

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

At its peak, AT&T outages reached 73,000 with service disruptions beginning around 3:30 a.m. ET.

“Some of our customers are experiencing wireless service interruptions this morning. We are working urgently to restore service to them. We encourage the use of Wi-Fi calling until service is restored,” AT&T said in a statement.

AT&T reported its network was restored Thursday afternoon.

“We have restored wireless service to all our affected customers,” the Dallas-based company said in a statement posted on its website Thursday afternoon. “We sincerely apologize to them.”

While Verizon and T-Mobile customers also reported outages, the companies confirmed they were not experiencing any issues.

“Verizon’s network is operating normally. Some customers experienced issues this morning when calling or texting with customers served by another carrier. We are continuing to monitor the situation,” Verizon said.

T-Mobile said it did not experience an outage.

“Our network is operating normally. Down Detector is likely reflecting challenges our customers were having attempting to connect to users on other networks,” T-Mobile said.

Downdetecor reported the top cities that had user-reported issues included Houston, Chicago, Dallas, San Antonio, NYC, Atlanta, Austin and Miami.

Some law enforcement agencies were alerting the public that they might be unable to contact 911 because of the outages.

Downdetector relies on sources including user-submitted errors to provide real-time information about the status of various websites and services.

Sen. Marco Rubio, R-Fla., said a hypothetical cyberattack could make the latest AT&T outage the least of the United States' problems.

The senator wrote on social media an exponentially higher amount of people would be affected by an attack from China during a hypothetical invasion of Taiwan.

For tips on how to navigate a phone service outage, click here.

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Editor's note: WPEC and The Associated Press contributed to this article.

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