Hackers can break into dozens of cars at a time with a gadget that costs just £30

High-tech thieves can use signal jammers to break into almost any modern car - and sometimes, dozens at a time.

Nearly every car in a Manchester carpark was left unable to be locked last Sunday, the Register reports, in an apparent signal jamming attack.

Any car that uses electronic locking is at risk of jammers. They work by jamming the radio frequencies used by car fobs to lock vehicles remotely. The locking signal is lost in the noise, leaving the driver unable to unlock the car.

The devices can't unlock cars if they've already been locked - and similarly if a vehicle also has a physical key, it can still be locked. But some cars rely exclusively on electronic locking (or don't use keys for their boots/trunks), making them impossible to secure if a jammer is nearby.

A video posted on Facebook by Autumn DePoe-Hughes shows exactly this: In a car park at a Manchester shopping centre earlier this week, numerous drivers are left standing helpless as they can't secure their cars, while car alarms blare constantly.

DePoe-Hughes subsequently told The Register that she was "there there for at least a half an hour and according to people around us, it had been going on before we got there. It was continuing as we left, so I don't know how long it continued on. The mall was closing up for the day and we had no way to secure the boot (trunk) of our car, so we left. We were unable to lock the car with the fobs throughout our time there and the same happened to those around us, including one very confused mother."

She added: "I went around speaking to people and they all confirmed that they could not lock their cars and couldn't figure out what was going on. They all thought their cars needed to be repaired."

The devices can be bought online for as little as £30, crime reduction specialist Darron Tickle told the Manchester Evening News last year. He also warned that if someone has used a signal jammer to steal things from your car, you may have difficulty claiming back insurance.

"Hopefully, you would notice your car hadn't locked," Tickle said. "But the problem we have is if you have something stolen from a vehicle and there's no sign of forced entry, you may struggle to get an insurance company to pay out, especially if there's no evidence of breaking in."

The potential uses of jammers go beyond vehicles. Anything that secures itself with radio signals - such as remote-controlled gate locks - are vulnerable to disruption.

We found multiple heavy-duty scanners for sale online for a few hundred dollars each: