T-Mobile revealed late on Thursday that the personal details of “a small percentage” of customers were exposed after hackers gained access to its systems.
According to the company, the attackers did not access payment card data, social security numbers (SSNs) or passwords. However, they may have stolen personal information such as names, billing zip codes, phone numbers, email addresses, account numbers, and account type. Impacted customers are being notified.
The data breach was discovered and shut down by T-Mobile’s security team on August 20. The company said it also reported the incident to authorities.
T-Mobile’s public statement provides no other details about the incident, but the firm’s representatives told SecurityWeek that the breach impacts roughly 3 percent of its 77 million customers, which represents approximately 2.3 million individuals.
“We always encourage customers to make sure they have PIN/passcodes on their accounts as well as a strong password, and to change their account passwords as well as the PIN/passcode frequently,” the company said in an emailed statement. “If any customers have questions or concerns they should feel free to contact our customer care team by dialing 611 from their mobile phones.”
T-Mobile also told Motherboard that the attackers were likely part of an international group and that they leveraged an API to access the company’s servers.
“This security incident favourably stands out among many others by prompt detection and transparent disclosure,” said Ilia Kolochenko, CEO of High-Tech Bridge. “Many of the recent data breaches, including the most disastrous ones, were discovered weeks ago but then announced months after the occurrence. T-Mobile serves as a laudable example of prompt incident response. This, however, does not absolve them from accountability for the breach and further cybersecurity enhancement to prevent similar incidents in the future.”
Related: Experian Hack Exposes Data of 15 Million T-Mobile Consumers
Related: T-Mobile ‘Incredibly Angry’ Over Breach via Credit Bureau