AT&T sent a letter (PDF) to affected customers to let them know what happened, what steps they can take to protect their information, and to apologize for violating its own privacy rules. The telecom is offering affected customers free credit monitoring service.
According to the letter, the employee in question would have been able to view personal account information details such as Social Security numbers and driver license numbers, as well as Customer Proprietary Network Information (CPNI), which is related to the telecommunications services that customers purchase from AT&T.
"On behalf of AT&T, please accept my sincere apology for this incident. Simply stated, this is not the way we conduct business, and as a result, this individual no longer works for AT&T," Michael A. Chiaramonte, Director of Finance Billing Operations for AT&T, stated in the letter.
Back in June, AT&T revealed that an insider exposed dates of birth and Social Security numbers in an effort to help resellers unlock/jailbreak AT&T phones so that they could be resold. This time around, it's not clear what the motive was.