(RNN) – An undisclosed number of AT&T mobile customers' personal data has been compromised by hackers, according to the Dallas Business Journal, who confirmed it with the telecommunications company on Friday.
The breach took place from April 9 to April 21, and was first disclosed in a filing with California regulators, a Better Business Bureau press release states.
The Business Journal said the breach was confirmed Friday, and the hackers are alleged to be employed by one of AT&T's service providers.
"We recently determined that employees of one of our service providers violated our strict privacy and security guidelines by accessing your account without authorization … and while doing so, would have been able to view your social security number and possibly your date of birth," AT&T said in a letter sent to customers this week.
The letter also said the data breach was "part of an effort to request codes from AT&T that are used to ‘unlock'" older phones in a "secondary mobile phone market … [and] then activated with other telecommunication providers."
AT&T did not state how many customers were affected during the April hack. California law requires that the business to notify their customers when more than 500 customers are at risk of a malicious security breach.
The letter also says that AT&T will provide a year worth of free credit report checks to affected customers and that they've notified law enforcement.
The process of "unlocking" mobile devices is helpful to consumers who want to take their device to a different carrier, or if their traveling outside of the U.S. American carriers have made it difficult for customers to do this, but made it available at the beginning or the end of two-year service contracts.
Some carriers even allow the purchase of unlocked devices at different prices.
The AT&T data breach follows the investigation of a possible security breach of the restaurant P.F. Chang's China Bistro which was originally reported on Wednesday.
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In a report filed in California this week, AT&T confirmed a data breach of mobile users in April. (Source: Flickr/Wesley Fryer/MGN Online)
