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Data held by one of the divisions of security firm Experian was hacked, and some information on a server that held T-Mobile US Inc. (NYSE: TMUS) data was compromised. For any T-Mobile customers who worry one of their files was hacked, the company has offered two years of free credit monitoring and identity tracking. As with many breaches, the offer to potentially affected customers does not appear meaningful compared to the threat.

T-Mobile’s CEO said:

I’ve always said that part of being the Un-carrier means telling it like it is. Whether it’s good news or bad, I’m going to be direct, transparent and honest.

We have been notified by Experian, a vendor that processes our credit applications, that they have experienced a data breach. The investigation is ongoing, but what we know right now is that the hacker acquired the records of approximately 15 million people, including new applicants requiring a credit check for service or device financing from September 1, 2013 through September 16, 2015. These records include information such as name, address and birthdate as well as encrypted fields with Social Security number and ID number (such as driver’s license or passport number), and additional information used in T-Mobile’s own credit assessment. Experian has determined that this encryption may have been compromised. We are working with Experian to take protective steps for all of these consumers as quickly as possible.

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Also:

Experian has assured us that they have taken aggressive steps to improve the protection of their system and of our data.

Anyone concerned that they may have been impacted by Experian’s data breach can sign up for two years of FREE credit monitoring and identity resolution services at www.protectmyID.com/securityincident.

And:

At T-Mobile, privacy and security is of utmost importance, so I will stay very close to this issue and I will do everything possible to continue to earn your trust every day.

Credit card and bank information were not taken. Some more important things may have been: names, addresses and Social Security numbers.

Experian management said it was sorry, and will try not to let it happen again.

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