The names, Social Security numbers and information from driver's licenses or other identification of just over 40 million people who applied for T-Mobile credit were exposed in a recent data breach, the company said Wednesday.

The same data for about 7.8 million current T-Mobile customers who pay monthly for phone service also appears to be compromised. No phone numbers, account numbers, PINs, passwords or financial information from the nearly 50 million records and accounts were compromised, it said.

T-Mobile has been hit before by data theft but in the most recent case, "the sheer numbers fa...