AT&T emails 70M customers, causes massive traffic spike at Experian. Here's what happened

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If you have a lot of customers you need to contact regarding an important communication, such as a data breach, it may be a good idea to stage those communications over several days rather than all at once. On April 11, AT&T began emailing 70M of its current and former customers affected by a data leak disclosed by the company on March 30.

Update: At 11:55 PM on April 11, AT&T said the company is staging email blasts to notify customers rather than sending out a single communication, as we wrote originally. “We have a rolling cadence on the emails to ensure our team and Experian can effectively service those impacted. We’re not aware of any issues currently, but you can check with Experian,” AT&T Director of Corporate Communications Dan Feldstein told ZDNET.

Also: AT&T resets passcodes for 7.6 million customers after data leak. What experts are saying

In the email, sent at 3:23 p.m. ET, presumably to tens of millions of its customers, AT&T says that a breach (which the company disclosed in a previous email on March 30) compromised customer information. The company said that financial details and call history remained secure.

In response, AT&T is resetting account passcodes and offering a year of free credit monitoring and identity theft protection via Experian’s IdentityWorks service. Experian is a large global credit reporting agency that provides data and analytical tools for credit and fraud monitoring, serving both individuals and businesses.

Jason Perlow/ZDNET

In the email, AT&T provides a free subscription code and a link to the Experian website for enrollment. When we attempted to enroll, we noticed that the server was performing extremely slowly and returning HTTP 500 errors, presumably due to the high levels of traffic AT&T’s email sent over. We also noticed that SMS credential logins stopped working via Experian’s mobile application.

Here’s the error message Experian’s website gave us. Jason Perlow/ZDNET

The subscription offer is genuine, and we were eventually able to log in after several minutes. Still, the website’s performance was agonizing. It took us over half an hour to add our account information for monitoring, experiencing multiple HTTP timeouts along the way.

Experian ID Works portal. Jason Perlow/ZDNET

The Downdetector service confirmed the traffic spike at Experian, showing a massive increase in user reports at around 5 p.m. ET.

Experian user downtime reports at Downdetector Jason Perlow/ZDNET

At 4:54 p.m. ET, Experian noted on X that its website had stabilized. However, as of 6 p.m. ET, the site remained non-responsive.

Update on Friday, April 12, at 12:28 AM: We’ve asked AT&T how many emails the company sent on April 11, and if they are staged, how many more traffic surges Experian can expect over the next several days.

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