On Monday, President Barrack Obama publicly confirmed during a news conference in Washington that the "lost" RQ-170 Sentinel had malfunctioned and was in the hands of Iranian authorities. "We have asked for it back, we'll see how the Iranians respond," he said.

The conference marked the first public admission by the Obama administration that the drone had not returned from its CIA spying mission. Iran claims the Sentinel was shot down, but the U.S. disagrees saying it malfunctioned, although no effort was made to explain how it appears to be intact.

Now it appears there could be a third plausible explanation, one that claims it never crashed after all. According to the Christian Science Monitor, Iran hijacked the pilotless vehicle by exploiting a known vulnerability with its GPS systems, which enabled them to command it to land in Iranian territory.

The communications between the Sentinel and its command center are encrypted, but jamming them was also possible. When the device loses contact with its instructors, it is programmed to fly to and land at a predetermined GPS location. The Iranian authorities appear to have used the flaw to send fake GPS parameters, essentially making the drone land exactly where they wanted it to.

Even more alarmingly, a publicly readable report published in 2003 highlighted that "GPS spoofing" was possible, and provided countermeasures for reducing the risk of it occurring. Yet despite the warnings, the U.S. military appear to have done nothing to counter the serious threat it poses. No doubt the Iranians also had a good read of the paper (PDF) published in October at a security conference, elaborating in detail on the tools needed to successfully "spoof" drones and airborne vehicles to seamlessly take them over.

The last few years have seen Iran suffer multiple setbacks, which some experts have suggested are the result of a covert war carried out by the U.S. and its allies. Recent happenings include the assassinations of nuclear scientists, random explosions at industrial facilities, and last year the Stuxnet worm deployed to destroy centrifuges at nuclear plants.