AT&T says customer data accessed to unlock smartphones

Personal information, including Social Security numbers and call records, was accessed for an unknown number of AT&T Mobility customers by people outside of the company, AT&T has confirmed.

The breach took place between April 9-21, but was only disclosed recently in a filing with California regulators.

While AT&T wouldn't say how many customers were affected, state law requires such disclosures if an incident affects at least 500 customers in California.

"Employees of one of our service providers violated our strict privacy and security guidelines by accessing your account without authorization," the company said in a letter to affected customers. "AT&T believes the employees accessed your account as part of an effort to request codes from AT&T than are used to unlock AT&T mobile phones in the secondary mobile phone market."