North Korea is believed to be the culprit behind recent data leaks on South Korea's nuclear power plants.
An interim probe by local authorities found that malicious codes used in the cyber attacks were similar to those used by North Korea in the past,... and that they originated from IP addresses in the North.
Pyongyang, through its Uriminzokkiri website, denied any involvement in the hacking.
Last week, a group of hackers that claimed to have leaked documents about the nuclear facilities in the past, released additional files... and demanded money in return for not selling the information to other countries.