The nation’s financial watchdog said Sunday that it would launch a special probe into Standard Chartered Bank Korea and Citibank Korea early next year over their “lax internal controls.”

The Financial Supervisory Service plans to look into the recent customer data leaks at the two foreign first-tier banks here, as well as restructuring and dividend payouts to shareholders abroad.

The move came after the FSS found the two banks responsible for the country’s largest-ever bank customer data leak of about 130,000 cases of sensitive customer data, which surfaced on Dec. 12.

Standard Chartered Bank Korea, the local operation of Britain’s banking group, had about 103,000 cases of core customer data leaked by an official of its partner company.

Citibank Korea, the local unit of the U.S. banking group, came under fire as one of its senior officials stole and delivered 34,000 cases of customer data to a loan collection agency.

The leaked customer data included social security numbers, workplaces and loan histories, which could be exploited for voice phishing, smishing and other deceptive crimes.

“We take it as an extremely dangerous situation, where the banks’ self-monitoring could fall short of sufficient oversight,” an FSS official said.

On Dec. 3, FSS Gov. Choi Soo-hyun urged executives of the foreign financial companies to have “strong internal controls.”

By Chung Joo-won (joowonc@heraldcorp.com)