What caused the AT&T outage? UT Dallas professor explains his theory

AT&T announced its wireless service was restored about 12 hours after an outage across the Dallas-based company's cell phone network.

Cell phone customers had their connected world stop at about 2 a.m. when people in North Texas began having phone problems.

The Dallas area was one of the hardest hit in the country, but outages were reported nationwide, including in Houston, Los Angeles, Chicago and Atlanta.

The White House said AT&T indicated it was not a cyberattack, with the FBI monitoring the situation as well.

There's no evidence it was the result of anything malicious, but it has shined a light on just how many services are affected when it goes down.

"Usually it is some kind of software bug that goes undetected and if you haven't properly tested it before release, it can have certain unforeseen outcomes," said Ravi Prakash, professor of computer sciences at University of Texas at Dallas.

Prakash lost phone service this morning too.

It is only his theory, but he feels the outage could have been sparked by a network software patch.

"Typically, you would push these kinds of patches late at night when there are very few customers online to provide minimum disruption," Prakash said.

Software patches to fix bugs happen all the time.

"We do get notifications for when you're updating your phone, but for the service providers, they're under no obligation to inform us that they're updating their own network," Prakash explained.

The network stands on three prongs.

The first carries voice and data from a phone to the wireless link and, ultimately, to another phone. He tested that and found it to be okay.

"I also made a call using my Microsoft Teams that UTD provides to my cell phone, which is a wireless service that worked! So that's why I'm saying maybe the coordinate work was fine," Prakash said.

The second component is location services, how providers know where you are and the tower you are on.

"Out of curiosity, I looked up my Life 360, Find My Phone. They were all showing my correct location and the correct location of my family, so I know that that service was working even though all of them were connected over Wi-Fi," said Prakash.

That leaves the third leg: the connection between your phone and the tower.

That's where he thinks the problem occurred.

"If that trust and identification doesn't work, then my phone is going to tell me that I can't find service," said Prakash.

Late Thursday night, AT&T posted an update saying the 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 its assessment of Thursday’s outage is ongoing at this time. 

North Texans react to AT&T outage

The outage caused a great deal of frustration for customers in North Texas and nationwide.

"I had to remember there was once upon a time there was a world with no cell phones, so I got to live that world for a couple of hours," said Eboni Ivory.

Many people started the day dealing with the issue.

"I woke up this morning and my cell phone had SOS on there, so it was clear it didn't have any service," said Sheri Winsper.

During the disruption, Winsper was worried about reaching her father.

"My husband and I, we haven't had our landline for a while because we never needed it, but I was able to call my dad because he is of the landline generation, so I was able to get ahold of him," she said.

Ivory was heading to pick up her cousin for her birthday.

"I had to actually pull over and connect to Wi-Fi at Starbucks to text her and let her know I am on my way, and she is an hour away from me," she said.

It's no secret we spend a little too much time on our phones.

The temporary case of the haves vs. have nots exposed just how reliant we are on them.

"I had to go from listening to Spotify to having to figure out what radio station to listen to because I had no means of communication with Spotify, friends, family, it was a little obnoxious," Ivory said.

The outage also affected businesses, and even first responders who rely on a key network tied to AT&T.

911 dispatch centers across the country reported an influx of people calling for no good reason.

In Tarrant County, some government operations were affected, including payment options for property taxes.

The Federal Communications Commission said the outage also affected AT&T's FirstNet.

It's a network AT&T has helped build and maintain for first responders, and even journalists. It’s designed to keep communication flowing during emergencies.