Keyless entry systems are not uncommon in cars these days but they are also the target of unscrupulous hackers who are able to spoof the signal from a car key fob to open a vehicle’s doors. Now, a group of researchers at the Beijing-based security firm Qihoo 360 has demonstrated that the attack is not only easy to execute, but can be done relatively cheaply as well.

Presenting their findings at the Hack In The Box Security Conference (HITBSecConf) in Amsterdam, the group (who called themselves UnicornTeam) said their relay hack allows them to steal cars parked more than a thousand feet away from the owner’s key fob.

A short video shows us how the attack is carried out, which involves two people. One hacker holds a device in close proximity with the victim’s key fob, capturing the radio signals transmitted from it. Meanwhile, the hacker’s accomplice will receive the signals on a separate device, sending it to the car, allowing him/her to unlock the doors.

The attack therefore tricks both the car and real key fob into thinking they’re in close proximity. This concept has been demonstrated before, although it previously involved just recording the radio signal, transmitting it, and playing it back.

UnicornTeam’s approach differs in that their custom devices are able to demodulate the signal, allowing them to send the decomposed signal bit by bit at a much lower frequency. This allows for signals to be sent further (up to 1,000 feet), compared to 300 feet as shown in past tests by other groups.

More impressively, the cost of the devices are revealed to be in the region of around 20 euros (RM94), according to their presentation slides, making them substantially cheaper than other devices. Also included is list of possible countermeasures to the attack, including placing the key fob in a Faraday bag and reducing the amount of time it takes before the car’s lock system times out.