According to Fox News, the researchers were able to hijack the drone and set it on a path of destruction (without actually destroying anything, mind you), by analysing the GPS signal the drone was locked in on, then sending a stronger signal for it to pick up on.
Initially, his signal matches that of the GPS system so the drone thinks nothing is amiss. That's when he attacks — sending his own commands to the onboard computer, putting the drone at his beck and call.
Obviously, it's not like anyone can do this. But the thought that a group of people with the proper collection of brains and resources could launch missiles from a drone (or turn a drone itself into a weapon) is a scary thought. [Fox News via Reuters]