The victims of a recent information leak from three credit card companies are believed to number about 15 million, officials and sources said Sunday.

The prosecution announced on Jan. 9 that it has charged three people with stealing private data of customers from three major card issuers ― KB Kookmin Card, NongHyup Card and Lotte Card ― in what is seen as the nation’s largest financial information leak.

The Financial Supervisory Service said that regulatory inspectors suspect that private information of clients of almost all commercial banks linked to the credit card firms have been leaked.

The victims are believed to include top government officials, lawmakers, senior corporate executives and celebrities, said FSS officials. Among them are the nation’s top two regulatory officials ― FSS governor Choi Soo-hyun and Financial Services Commission chairman Shin Je-yoon.

The supervisory officials said the damage was greater because the banks and card companies share information about their clients.

“The sister firms (KB Kookmin Bank and KB Kookmin Card) share customer information,” an official said. “NongHyup Bank is also believed to have suffered the chain effect in the wake of the leaks at its credit card subsidiary, NongHyup Card.”

In addition, three other major banks ― Woori, Hana and Shinhan ― could also be affected by the leaks as they offered credit card settlement accounts to a large portion of card holders of KB Kookmin, NongHyup and Lotte.

Officials estimated that the number of victims of the leaks at the three card firms came to about 15 million, which is equivalent to 70 percent of the nation’s total cardholders.

When the cases of overlap (a consumer holding several different cards and bank accounts) were not taken into consideration, the number of cases of personal information theft surpassed 100 million, they said.

The detailed personal data included customers’ credit scores, ceiling for monthly credit card use, marital status and whether they own automobile or not.

The FSS will send inspectors to financial companies to look into their internal control systems.

The state regulatory agency told reporters that punitive measures against the three firms and their chief executives would be inevitable.

On Sunday, an emergency meeting was convened at the head office of KB Financial Group in downtown Seoul. Participants included group chairman Lim Young-rok, bank unit CEO Lee Kun-ho and credit card unit CEO Shim Jae-oh.

KB spokespeople said the management discussed ways to minimize the damage, adding that the group plans to thoroughly compensate the victims.

Over the past few years, the financial industry has come under severe criticism due to a series of hacking incidents. Among the firms that lost personal information were Hyundai Capital, Samsung Card, Hana SK Card and NongHyup Financial Group.

By Kim Yon-se (kys@heraldcorp.com)