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.
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.
North Korea has some of the most isolated communications networks in the world. Just owning a computer requires police permission, and the open Internet is unknown except to a tiny elite. The country has one main conduit for Internet connections to the outside world, through China.
In contrast, Iranians surfed the Net broadly and had interactions with companies from around the globe.
A spokeswoman for the NSA declined to comment for this story. The spy agency has previously declined to comment on the Stuxnet attack against Iran.
The United States has launched many cyber espionage campaigns, but North Korea is only the second country, after Iran, that the NSA is now known to have targeted with software designed to destroy equipment.
Washington has long expressed concerns about Pyongyang’s nuclear program, which it says breaches international agreements. North Korea has been hit with sanctions because of its nuclear and missile tests, moves that Pyongyang sees as an attack on its sovereign right to defend itself.
U.S. Secretary of State John Kerry said last week that Washington and Beijing were discussing imposing further sanctions on North Korea, which he said was “not even close” to taking steps to end its nuclear program.