A senior database administrator at a subsidiary of Fidelity National Information Services who was responsible for defining and enforcing data access rights at the firm took data belonging to as many as 8.5 million consumers – not 2.3 million, as originally disclosed by the company.

The new number was disclosed in filings by Fidelity National with the US Securities and Exchange Commission (SEC). The company warned of the possibility that even more data may have been compromised in the breach. Fidelity National, which is not connected with the more widely known mutual funds company Fidelity Investments, is a transaction processing and outsourcing services provider to the financial industry.

On July 3, Fidelity National disclosed that a database administrator, who is no longer with the company, had illegally downloaded and sold customer data to a data broker. The data broker, in turn, sold a subset of the data to other direct marketing companies. The stolen data included names, addresses, birth dates, bank account and credit card information, the company said.

The database administrator worked for Certegy, which provides a check-authorisation service to help merchants decide whether to accept checks as payment for goods and service.

In its SEC filing, Fidelity National said that an investigation into the theft by the employee showed that 8.5 million records were stolen. Of that number, about 5.7 million records were checking account records and about 1.5 million records included credit card details. The remaining records contained only identifying information such as names, addresses, dates of birth and telephone numbers.

“This is an incremental increase of approximately 3.5 million checking account records and approximately 1.4 million credit card records over our announcement on July 3, 2007,” Fidelity National said in its statement. Fidelity added that a portion of the stolen data was taken from the company’s credit card issuance business.

Fidelity said it “continues to see no evidence of the stolen information being used for anything other than marketing purposes. Although the company does not anticipate significant liability to consumers or for financial fraud, there can be no assurance that this matter will not result in fines or other consequences that adversely impact the company or its relationship with governing organisations, customers or regulators.”