How to protect your keyless car from a relay attack

Stealing your fancy new car shouldn't be easy, but as a recently published video filmed in September reminds us, it all too often is. That's because, it turns out, the very same wireless key fob designed to unlock and start your shiny vehicle can be turned against you by those looking for a gone-in-under-60-seconds score.

But here's the thing: While the car-jacking technique in question is relatively straightforward to pull off, it's also simple to fight against. All it takes is a little bit of precaution and you can sleep easy knowing your four-wheeled friend is safe and sound.

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The method in question is called a relay attack, and, while not a new threat, it's once again on the minds of worried car owners following the filmed theft of a Mercedes-Benz in the UK. In the video, two criminals can be seen rolling up to a parked car, fiddling with two devices, and then making their escape. The video is 86-seconds long, but the crime itself took even less time.

So how did they do it? While the exact tools used by the two bandits are unclear as the individuals remain at large, the general principle is well understood. Essentially, a device — in this case held by one thief next to what appears to be a garage door — searches for, finds, and relays a signal from a wireless key fob inside the victim's home. That signal is sent to a second device, held by another thief, near the car itself. The car is tricked into thinking the fob is present, and is then able to be both unlocked and started.

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These devices have been spotted for sale online, so it's not like it takes a mechanical wizard to build one from scratch.

Importantly, they only work on cars that have a keyless ignition system — one that allows a driver to start the car by pushing a button after the vehicle detects a key is present. The attack would not start cars with a keyed ignition that just have a click-to-unlock fob.

So how to stop this? Thankfully, it's pretty easy. For the device to be able to relay the signal from the legit fob, it first must be able to detect it inside the house. Keeping your key fob in a Faraday sleeve — a pouch designed to block radio transmissions — would do this. These are available online, although you'll want to do some shopping around as some work better than others.

Essentially, you just need to make sure wherever you store your keys at night happens to include said Faraday sleeve. And, if during the day, you keep your car keys in a purse or a jacket pocket, add a second Faraday sleeve to the mix. After all, when it comes to protecting your fancy new wheels, what's another $100 in the scheme of things?

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