Researchers Commandeer Military Drone

That's a problem, they say, because as the use of military-grade drones becomes more fashionable here at home, terrorists who obtain the capability to intercept them could then turn them into guided missiles and use them as weapons, imitating the 9/11 attacks on a smaller, but more frequent, scale.

In a recent test initiated by the Department of Homeland Security, the UT researchers proved they could intercept a drone's GPS signals and take it over with a technique known as "spoofing." The high-tech hijacking procedure is described as "the transmission of matched-GPS-signal-structure interference in an attempt to commandeer the tracking loops of a victim receiver and thereby manipulate the receiver's timing or navigation solution," according to Prof. Todd E. Humphreys, who led the research team.

Spoofing goes way beyond jamming

Some experts have suggested that's how Iran managed to bring down a U.S. stealth RQ-170 drone hovering over its territory in 2011. One of the most sophisticated intelligence assets in the nation's arsenal, Iran said initially that it shot down the craft, but an increasing number of experts believe its GPS signal was either jammed or "hijacked," allowing Iran to intercept the aircraft intact.

"Spoofing a GPS receiver on a UAV is just another way of hijacking a plane," said Humpheys, of UT-Austin's Radionavigation Lab.

Spoofing goes beyond simple jamming of GPS signals and has a much more diabolical potential. Jammers simply scramble or muddle signals, but spoofers are a quantum leap in technology because they are capable of manipulating computers which navigate the drones by using false information that, for all intents and purposes, looks real to the craft.

Humphreys' spoofer – which he called the most advanced ever built – is capable of infiltrating a drone's GPS system with a signal more powerful than the one it receives from GPS satellites hovering above the earth.

He says initially his spoofer sends a signal that matches the GPS signal being transmitted to the drone by its operator, so the craft doesn't know the difference. From there, he implements his own flight plan and commands to the drone's on-board computer, effectively hijacking it.

That's a very serious situation, he told Fox News.

"In five or 10 years you have 30,000 drones in the airspace. Each one of these could be a potential missile used against us," he said.

Currently, drones do not operate broadly in U.S. airspace, but that's a trend that is about to change.

Infrastructure vulnerable as well

In February, amid pressure from the Defense Department and drone makers, Congress ordered the Federal Aviation Administration to develop regulations permitting government and commercial use of drones over American soil and cities by 2015.

Eventually, under the plan, scores of government and police agencies, as well as commercial interests and colleges, will be utilizing unmanned aerial vehicles (UAVs) for dozens of uses: monitoring power and oil lines; conducting search-and-rescue missions; and, of course, engaging in "authorized" surveillance.

The future may also see pilot-less cargo planes guided by GPS – all signals that can be hacked and stolen by innovative terrorists.

Moreover, Humphreys and his fellow researchers note, American infrastructure currently relies on GPS signals and will rely on them more so in the future, exposing another potential vulnerability.

At present, for example, cell phone towers "rely on GPS timing for tower-to-tower synchronization," the UT professor notes. Spoofers could disrupt that synchronization process by as little as 10 microseconds, which would disrupt the hand-off of calls from one tower to the next.

Also, the nation's power grid of the future will rely on GPS time stamps, he said. Spoofers theoretically could disrupt the time stamp process, which would cause electrical plant operators to adjust output up or down, depending on the perceived need. That "could distort power flow or stability estimates in such a way that grid operators would take incorrect or unnecessary control actions including powering up or shutting down generators, potentially causing blackouts or damage to power-grid equipment," he wrote.