T-Mobile and Experian said the breach subjected the private information to hackers for a period of two years.
Experian said it immediately began investigating the matter, but noted that the breach did not impact its consumer credit bureau.
“The data acquired included names, dates of birth, addresses, and Social Security numbers and/or an alternative form of ID like a drivers' license number, as well as additional information used in T-Mobile's own credit assessment. No payment card or banking information was acquired," the credit bureau said in a news release.
Anyone who applied for T-Mobile service in the United States between September 1, 2013 through September 16, 2015 is potentially affected, officials said. Experian and T-Mobile said they will provide two years of free credit monitoring for those customers.
