Millions of South Koreans hit by credit card hack

Credit card details from almost half of all South Koreans have been stolen and sold to marketing firms. The data was stolen by a computer contractor working for a company called the Korea Credit Bureau that produces credit scores. The names, social security numbers and credit card details of 20 million South Koreans were copied by the IT worker.
Background:
Credit card details on 20 million South Koreans stolen [BBC]
Bank data of 20 million customers leaked in South Korea [ZDNet]
17-year-old created malware used in Target breach: report [Atlanta Journal-Constitution]