In 2010, the US National Security Agency tried to use the Stuxnet worm against North Korea, which was used to stop uranium enrichment centrifuges in Iran. However, this attempt was unsuccessful.
The hackers were unable to get to the computers that control nuclear facilities in the DPRK, as they were well isolated from the outside Internet. The NSA declined to comment on the operation.
According to Reuters, in the DPRK there is no open access to the Internet, while in Iran it is much more widespread. At the same time, North Korea uses approximately the same equipment in the nuclear field as Iran: computers run on Windows, and centrifuge control equipment is developed by Siemens. It was for these systems that the Stuxnet virus was developed.
Since the systems were similar, if Stuxnet had been able to implement it, he wouldn't have had to mess around with Korean programs for a long time (eng. lang.)