Computer networks at major South Korean banks broke down simultaneously on Wednesday, prompting the financial watchdog to launch an investigation to determine the cause and raise its crisis alert level by one notch. According to bank officials and the Financial Supervisory Service (FSS), Shinhan Bank, the flagship unit of the country\'s No. 3 banking group Shinhan Financial Group Co., experienced interruption in its electronic transaction system around 2 p.m., including Internet banking, smartphone banking and use of automated teller machines.