Keyless car theft explained: how relay attacks work and how to stop them

If your car unlocks when you walk up to it with the key in your pocket, this article is about you.

How a relay attack works

Keyless entry works by conversation. Your car constantly asks a quiet question — is my key nearby? — and your fob answers. If the answer comes back, the doors unlock and the start button works.

The car cannot tell how far away the fob really is. It only knows it got an answer.

A relay attack exploits exactly that. It usually takes two people and two devices:

1. One person stands close to your house — by the front door, a window, a porch — with a device that picks up the faint signal from your keys inside.
2. That signal is relayed to a second device held next to your car.
3. The car hears what it believes is your key standing right beside it, and unlocks.
4. The same trick lets the engine start.

Nothing is smashed. No alarm goes off. From the outside it looks exactly like the owner getting into their own car.

Why the usual advice is not enough

Putting your keys in a metal tin, in the microwave, or upstairs at the back of the house are all attempts at the same idea: put distance or metal between the fob and the street. They work inconsistently, and they rely on you remembering every single night.

The fix that actually works

A Faraday pouch is a small bag lined with a conductive layer that blocks radio signals from getting in or out. Put the fob inside, close it fully, and the conversation stops. The car asks its question and nothing answers.

It is genuinely that simple — and it costs less than a tank of fuel.

Test yours in ten seconds

Put your fob in the pouch, close it properly, and walk up to your car with it. If the doors do not unlock and the start button does not respond, the pouch is doing its job. Do this when you first get one, and again occasionally — a pouch that has been sat on for two years may have a worn lining.

Three habits worth building

• Both fobs, every time. The spare in the kitchen drawer is just as relayable as the one in your pocket. Most homes need two pouches, which is why we sell them two for £15.
• Close it fully. A pouch left half open blocks nothing.
• Add a physical layer. A pouch stops the electronic way in. A steering lock stops the car being driven away, and is visible from the pavement before anyone tries.

Together, that is both doors closed.