( CNN ) -- Police have arrested two people in connection with a cyber-attack that yielded personal details for 12 million customers of one of South Korea 's biggest phone companies . One of the suspects , identified only by the surname Kim , used his own customized hacking program to break into the computer system used by KT Corp , Incheon Metropolitan Police Agency Commissioner Lee Sang-Won said in a statement obtained by CNN Thursday . Kim , whom police said was 29 year old , accessed bank details , home addresses and employment information for three-quarters of KT 's 16 million registered users . This data was sold on to a 37-year-old man identified only as Park . The owner of a telemarketing business , Park used this information to sell cell phones posing as a KT representative , police said . The two made 11.5 billion won ( US $ 10.8 million ) from the scheme , which dated back to February 2013 , police added . A third person initially implicated in the case was released . The investigation is now expanding to other hacking activities and other cell phone sales stores . KT said in a statement that it would actively cooperate with the police investigation to `` minimize the damage to its customers , '' and `` figure out the route of information leakage . '' Credit card scam . In January this year , the personal data for 20 million South Korean credit card customers was stolen by a worker at the Korea Credit Bureau -- a company that offers risk management and fraud detection services . The worker , who had access to various databases at the firm , is alleged to have secretly copied data onto an external drive over the course of a year and a half . Clients of three Korean companies -- KB Kookmin Bank , Lotte Card and Nonghyup Bank -- were hardest hit by the data theft . Following this leak , financial regulators have been working to revise legislation to beef up the protection of personal information , the Yonhap news agency reported .
NSA obtained details for 12 million customers of South Korean telecommunications giant . Bank details , home addresses obtained for three - quarters of SK Telecom 's users . Details used by an accomplice to sell cell phones posing as KT representative . Second major data leak in South Korea since September .