AT&T has admitted that a former employee gained access to a limited amount of customer information including social security numbers and drivers' license numbers.

The security breach, first reported by Threatpost, occurred in August, according to a form letter from AT&T posted by the Vermont Attorney General's office. The letter explains that the breach was the result of an AT&T worker who accessed customer accounts without authorization. AT&T did not say how many accounts had been compromised.

AT&T's letter stated that the company is reversing any unauthorized charges, offering a year of free credit monitoring to those affected and notifying federal agencies about the issue. The employee has been fired.

"We take our customers’ privacy very seriously and value the trust they have in us," AT&T wrote in a statement. "Unfortunately, we recently learned that one of our employees did not follow our strict privacy rules and inappropriately obtained some customer information. This individual no longer works at AT&T and we are directly contacting the limited number of affected customers."

Re/code reported that around 1,600 customers are at risk, a number that a source at AT&T confirmed to Mashable. This makes it a much smaller security issue than other recent breaches. A Home Depot security issue compromised many millions of cards.