T-Mobile says hacker gained access to employee email accounts, user data

This is the second security breach T-Mobile discloses in the last six months, after a first incident in November 2019.

T-Mobile

Image: T-Mobile, ZDNet

US telecommunications giant T-Mobile disclosed yesterday a security breach that impacted both its employees and customers alike.

In data breach notifications posted on its website, the company said that its security team has recently stopped "a malicious attack" against its email vendor.

The attack was successful, T-Mobile said, and the hacker (or hackers) gained access to "certain T-Mobile employee email accounts, some of which contained account information for T-Mobile customers and employees."

The company said it believes the hacker might have used this access to steal data on T-Mobile employees and some of its customers.

"Information accessed illegally may have included names and addresses, phone numbers, account numbers, rate plans and features, and billing information," T-Mobile said.

For some users "Social Security numbers, financial account information, and government identification numbers" were exposed, while for others, this data was not.

The US telco is currently sending out SMS notifications to all impacted users. Users who had just account data and those who had financial data exposed are getting different notifications.

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Image via u/bahamapapa817 on Reddit

T-Mobile did not say how many users were impacted but recommended that customers change the personal identification number (PIN/passcode) on their T-Mobile accounts.

Current and past customers were impacted alike.

This is the second security breach T-Mobile discloses in the past six months. It disclosed a similar security breach in November 2019. At the time, T-Mobile said the incident only impacted a small number of customers of its prepaid service.

Sprint also disclosed two security breaches last year, one in May and a second in July.

T-Mobile did not return a request for comment seeking additional details about the incident.