T-Mobile promises that no financial data, credit card information, social security numbers, or passwords were compromised in the breach. However, "some of your personal information may have been exposed," the company states in the letter shared online, including one or more of the following: name, billing zip code, phone number, email address, account number, and account type (prepaid or postpaid).
A T-Mobile spokesperson says that the security breach affected "slightly less than" three percent of its 77 million customers, but did not reference a specific number. The incident reportedly happened "early in the morning" on August 20, and was perpetrated by hackers part of "an international group" that accessed T-Mobile servers through an API that "didn't contain any financial data or other very sensitive data."
The intrusion was discovered by T-Mobile's cybersecurity team the same day:
“We found it quickly and shut it down very fast,” the spokesperson said.T-Mobile is now reaching out to notify all affected customers, and "if you don't receive a notification then that means your account was not among those impacted by this incident." The breach occurred less than a week after T-Mobile announced its new customer service initiative "Team of Experts."
The spokesperson said she couldn’t give “specifics” of the attack and did not know whether the hackers were criminals or part of a government.
T-Mobile is reaching out to victims directly via text message to notify them, she said.