Prime Minister Chung Hong-won instructed the financial watchdog chief Monday to sternly punish those responsible for a recent massive leak of personal information of credit card users, calling for fundamental measures to prevent recurrence. According to the prosecution, sensitive personal information, including resident registration numbers, bank account numbers and credit ratings, of as many as 104 million customers were leaked altogether from the country's major credit card firms of KB Kookmin Card Co., NH Nonghyup Card Co. and Lotte Card Co.