Two security experts in America have demonstrated how they can take control of a standard car using computer software and a laptop.
Once 'hacked' into the car's ECU, the technical whiz kids can not only steer the vehicle but also alter throttle inputs and mess around with fuel displays and other digital read-outs.
Charlie Miller and Chris Valasek were demonstrating their discovery ahead of security conference Defcon in Las Vegas in August. They told the BBC they hoped to raise awareness about the security issues around increasingly computer-dominated car control.
The car 'hack' was achieved by connecting a laptop to the electronic control units (ECUs) of a 2010 Ford Escape and a Toyota Prius of the same year via the diagnostics port.
Many modern cars use ECUs as part of the overall computer network that controls acceleration, braking, steering and even the horn.
The computer scientists were able to write specific software that overrides instructions from the driver, seizing control of the vehicle via a video game console joypad.
A spokesman for Toyota told the BBC that because the hardware had to be physically connected inside the car, he did not consider it to be "hacking".
"We don't consider that to be 'hacking' in the sense of creating unexpected behaviour, because the device must be connected - i.e. the control system of the car physically altered.
"The presence of a laptop or other device connected to the OBD [on board diagnostics] II port would be apparent."
Valasek disagrees, and believes that all you would need is brief access to the ECU to change many vital settings and completely reprogram the vehicle.
He told AFP: "We disengaged the brakes so if you were going slow and tried to press the brakes they wouldn't work. We could turn the headlamps on and off, honk the horn. We had control of many aspects of the automobile."
Mr Miller and Mr Valasek intend to make their research openly available following the conference.
"The information will be released to everyone. If you're just relying on the fact people aren't talking about the problem to stay safe, you're not really dealing with the problem," said Mr Miller.