"In 5 or 10 years you have 30,000 drones in the airspace,” he said. "Each one of these could be a potential missile used against us."
Both the U.S. and the U.K. have programs run by various law enforcement agencies to try to track down GPS signal jammers – at DHS under the Patriot Shield and Patriot Watch programs and under the Sentinel program in the U.K., IEEE Spectrum reported.
Robot- and unmanned-vehicle manufacturers are also working on an anti-spoofing technology it calls SAASM – Selective Availability Anti-Spoofing Module – which the U.S. military is already using in Afghanistan to keep Predator and other drones from being hijacked.
Other preventative measures include radio-beacon backups to keep the drone from getting confused by a single false signal, or inertial systems that create real-time dead-reckoning estimates of the drone's location to reality check the GPS, according to a letter the Association of Unmanned Vehicle Systems International (AUVSI) wrote to Spectrum after publication of its initial story June 26.
Not only are manufacturers trying to harden drones against spoofing, they continue to promote the safety/backup role of drone pilots, who are much less easily fooled than the drones themselves.
"While an aircraft itself may be unmanned, a trained professional is behind the controls, ready to respond, and bring a safe resolution to any problem that may arise," the letter read, in part.
Humphreys and his research team, meanwhile have published a number of papers describing spoofing techniques and countermeasures, as well as descriptions of how GPS spoofing works and how to manage it on your own.
Without some form of resistance to spoofing, the intelligence to respond effectively to a loss of remote control – rather than crashing or just flying in a straight line until it does – putting 30,000 drones in the skies over the U.S. would put every drone and every American over whom it flies in serious danger, Humphreys said.
"Spoofing a GPS receiver on a UAV is just another way of hijacking a plane," Humphreys told Fox News.