Stuxnet—the secretive digital weapon developed and deployed by the United States and Israel to knock out Iranian nuclear centrifuges—was not an only child, according to a new report. The computer worm, which was discovered in 2010, had a sister piece of computer malware that was designed to bring down North Korea’s nuclear program, too.
The twin virus was designed to activate once it came across Korean-language settings on affected machines, reports Reuters, citing an unnamed source. The plot fizzled, however, when the agents behind it failed to infect the machines running Pyongyang’s nuclear weapons program.
The attackers hit roadblocks, such as the “utter secrecy” within the hermit kingdom and “the isolation of its communications systems,” according to Reuters, citing another unnamed official. Indeed, North Korea is one of the most technologically remote countries on the planet.
“The United States has launched many cyber espionage campaigns,” writes Reuters reporter Joseph Menn, “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.”
The National Security Agency declined Fortune‘s request for comment. For more details, read the Reuters report here.
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