"In 2010, 50 nuclear-armed Minuteman missiles sitting in underground silos in Wyoming mysteriously disappeared from their launching crews’ monitors for nearly an hour. The crews could not have fired the missiles on presidential orders or discerned whether an enemy was trying to launch them. Was this a technical malfunction or was it something sinister? Had a hacker discovered an electronic back door to cut the links? For all the crews knew, someone had put all 50 missiles into countdown to launch. The missiles were designed to fire instantly as soon as they received a short stream of computer code, and they are indifferent about the code’s source.
It was a harrowing scene, and apprehension rippled all the way to the White House. Hackers were constantly bombarding our nuclear networks, and it was considered possible that they had breached the firewalls. The Air Force quickly determined that an improperly installed circuit card in an underground computer was responsible for the lockout, and the problem was fixed.
But President Obama was not satisfied and ordered investigators to continue to look for similar vulnerabilities. Sure enough, they turned up deficiencies, according to officials involved in the investigation.