The United States tried to deploy a version of the Stuxnet computer virus to attack North Korea's nuclear weapons program five years ago but ultimately failed, according to people familiar with the covert campaign.
The operation began in tandem with the now-famous Stuxnet attack that sabotaged Iran's nuclear program in 2009 and 2010 by destroying a thousand or more centrifuges that were enriching uranium. Reuters and others have reported that the Iran attack was a joint effort by U.S. and Israeli forces.
According to one U.S. intelligence source, Stuxnet's developers produced a related virus that would be activated when it encountered Korean-language settings on an infected machine.
But U.S. agents could not access the core machines that ran Pyongyang's nuclear weapons program, said another source, a former high-ranking intelligence official who was briefed on the program.
The official said the National Security Agency-led campaign was stymied by North Korea's utter secrecy, as well as the extreme isolation of its communications systems. A third source, also previously with U.S. intelligence, said he had heard about the failed cyber attack but did not know details.