JACKSONVILLE, Fla. — The latest disclosure of data from a credit card processing firm was discovered because an irate consumer complained to one of her venders about how much junk mail she was receiving.

According to Michelle Kersch, a vice president with Fidelity National Information Services, FIS became aware of the potential breach in its security after being contacted by one of its retail clients which used it Certegy Check Services check authorization service. Kersch said that the retailer had been contacted by one of its customers who was irate over how much junk mail they received after every time they shopped at that store.

Since the retailer knew it had not shared any of the customers' information, the information must have come from Certegy. After confirming that it did had not been hacked from outside, FIS launched an internal investigation which eventually pinned the blame on a nine-year database administrator who has since been fired.

Kersch said the administrator, named William Sullivan, was one of five administrators who had that level of access to the company's data and that FIS had acted to strengthen its internal controls by removing laptops from database administration, disabling the ability to download data to third party devices such as flash drives and instituting spot checks on computers with high access to data.