Thatcham Research assessed the vulnerability of cars to computerised theft, where criminals hack the key fob signal to enter and start a vehicle. Keyless car entry systems let drivers open and start their cars without taking their key out of their pocket. Thatcham looked at how susceptible new car models were to so-called "relay attacks", where thieves boost radio signals between the car and a key fob in a house to unlock and start the car. One criminal will hold a device close to the car that boosts the signal meant for the key, while the other thief will stand close to the house with another device that relays that signal to the key, fooling the system. Car industry body the SMMT said it had "serious concerns" about Thatcham's rating system. The US car giant recommended people double-lock their cars, and store their keys in a "suitable metal box" that will block radio signals.