Driverless cars can be tricked with simple stickers on road signs

Driverless cars may be the future of our transport infrastructure, but they carry with them a long list of engineering and security challenges to master before they'll hit our roads en masse.

While many of those are based around complex technical issues, one very low-tech security risk has been identified that could cause havoc with driverless cars.

Stickers. Yep, simple stickers, applied to road signs, could be a major danger for driverless cars, with road furniture a potential offline target for computer-guided vehicles.

A sticky problem

Security researchers at the University of Washington found that by using stickers made with just a home printer, they could confuse the computer vision systems of driverless cars, causing them to incorrectly read road signs.

Driverless cars use an object identifier and a classifier to make decisions when on the road – the first spotting things like pedestrians, signage and other vehicles, the second running the images past a neural network database that processes exactly what is being seen based on a huge number of previously-defined road images. The driverless car should then react according to the rules defined by the law, in accordance with what the two systems have seen.

But while the human eye can usually identify a sign that may have been tampered with (providing it's not been swapped out entirely), a few well placed stickers can trick the driverless car systems. In one instance, the researchers made what was clearly a standard stop sign read as a 45mph speed limit sign instead, with just a few well placed stickers.

“We [think] that given the similar appearance of warning signs, small perturbations are sufficient to confuse the classifier,” wrote researcher Yoshi Kohno. “In future work, we plan to explore this hypothesis with targeted classification attacks on other warning signs.”

Driverless dangers

While much of the trepidation around driverless cars sits with the potential to hack networked online vehicles for nefarious means, it wouldn't require much skill to cripple an entire road network reliant on driverless cars with this method of attack.

While the most violent examples would be to have driverless cars run stop signs, a driverless car's ability to read other road dangers (a crashed vehicle, for instance) and respond in kind could prevent catastrophic pile-ups from occurring.

What could cause more chaos, however, would be a more gentle approach – imagine a few tactically-changed road signs at major locations, leading to city-wide gridlock.

Contextual awareness for the vehicles will therefore be needed – whether that's the ability to communicate with official road maintenance services to double check any planned construction work and altered signage, or the ability to discern that, for instance, a dead-end short cul-de-sac probably shouldn't have a speed limit of 100mph.