How to block my car key signal to prevent keyless vehicle theft

KEYLESS cars, which allow the doors to be locked and unlocked by touching the door handle (or even simply approaching it) while the fob is in your pocket or bag, are brilliantly convenient, especially if you have your hands full of shopping or are carrying a child.

But with this smart technology has come a higher risk of the car being stolen, as tech-savvy criminals have developed ways to trick the car into unlocking and starting (read more here). For that reason, you may want to know the best way to block the signal from your car key.

You won’t be alone: although the number of car thefts overall fell in 2020, due to coronavirus lockdowns, since the easing of restrictions the number of stolen vehicles has soared. This is on top of trends leading up to 2020 that had seen car thefts in London rise by some 256% since 2016 and by 100% in Birmingham, Nottingham and Greater Manchester.

But, just as criminals have found a way to exploit this keyless car technology, there’s still plenty that motorists can do to prevent their pride and joy being snatched away.

How does keyless car theft work? 

Keyless cars use a number of methods but most of them rely on short-wave radio signals that alert the car to the fob’s presence when  it is within range (usually no more than a metre or two), allowing the doors to be opened and for it to be started up, once the fob is inside the vehicle.

The most common form of keyless car theft involves signal relaying. Thieves use a device, which can be bought cheaply online, to capture the signal from the key fob inside the owner’s house, for example, and boost it to a receiver held by an accomplice standing next to the car. This tricks the vehicle into thinking that the fob is closer than it is. The car can then be opened and driven away simply by pressing the starter button. A blank key fob can later be easily programmed to work with the car.

How can I block my car key signal? 

The single best way to prevent keyless theft is to block the signal being emitted by the key fob. While some manufacturers — Mercedes and Subaru, for instance — allow drivers to turn off their key fobs once they’re out of the car, for other drivers there’s a good alternative.

When at home, storing keys in a metal-lined “Faraday box” or pouch will block the signal being sent out from your key fob, thus preventing thieves from being able to capture it. Although metal tins in the house are usually an effective solution, a dedicated Faraday pouch may be more portable and can prevent signal relay theft while away from home. There are also ones that protect modern bank cards and smartphones from the same relay-based security threat.

It’s important not to assume that the box or pouch works, however. Make sure to test it by checking whether your car doors still open when the fob is inside the pouch.

Does tin foil block a car key signal? 

While tin foil does have some effect, it may only dampen the signal rather than blocking it fully, so a Faraday pouch or box is a better option than either tin foil or some of the more anecdotal solutions, such as keeping the fob in the microwave or fridge (which may result in a disaster for the fob’s battery).

Where can I get a signal blocker? 

Signal blocking pouches, bags and boxes aren’t expensive and they’re easy to come by. Prices typically start from less than £5 though they can rise to £100 and more depending on the size and finish. Always check before purchase that the dimensions will allow you to use it for what you need, i.e. that it’s large enough to accommodate your key fob.

From Halfords, this pouch is both inexpensive and has had good reviews while, from Argos, this Faraday box is also a good shout for home storage.

In what other ways can I prevent car theft? 

While signal blockers are a good way to prevent key fob hacking, some of the old-fashioned methods can be just as effective when it comes to protecting your belongings. Steering wheel locks mean that even if a thief manages to break into a car, they can’t drive it away.

It’s also a good idea not to keep valuables in the car and, if you have to do so, keep them out of sight in the boot; it may help prevent an opportunistic break-in. Fitting your car with a tracking device will also aid in recovery if the car is stolen.

What do the police say?

Keyless car theft has become such an issue that the police has issued specific advice on the matter.

The National Police Chiefs’ Council lead for Vehicle Crime, Assistant Chief Constable Jenny Sims, has advised that she “would urge drivers to take simple steps to keep their vehicle safe like storing your keys in metal tins or protective pouches that block the devices criminals are using. A return to basics like making sure your car is locked is worthwhile too. We know from research that some owners think that cars automatically lock – they don’t. Always double check before you walk away that it’s locked.”

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