Global information services group Experian announced Thursday that one of its business units had been hacked. The breach occurred on a server that contained data on behalf of one of its clients, T-Mobile.
The data includes personal information for a combination of about 15 million customers and applicants in the U.S. who at one point may have applied for T-Mobile service. The company said that the incident did not impact its own consumer credit database.
The data also included applicants requiring a credit check for service or device financing from Sept. 1, 2013 through Sept. 16, 2015, Experian North America said in a statement.
The ADRs of Ireland-headquartered Experian closed Thursday up nearly 1.7 percent to $16.38, while shares of T-Mobile were down more than 1 percent in extended trading.
In a letter to consumers, T-Mobile CEO John Legere said the following:
"Obviously I am incredibly angry about this data breach and we will institute a thorough review of our relationship with Experian, but right now my top concern and first focus is assisting any and all consumers affected. I take our customer and prospective customer privacy VERY seriously. This is no small issue for us. I do want to assure our customers that neither T-Mobile's systems nor network were part of this intrusion and this did not involve any payment card numbers or bank account information."