What Is a Relay Attack — and How Do You Stop It?
A relay attack is the technique behind most modern car thefts. It needs no key, no force and leaves no damage — which is exactly why it has become so common. Here's what's really happening.
Two people, two devices, under a minute
Your keyless fob constantly emits a low-power signal so the car can detect it when you're close. In a relay attack:
- One thief stands near your home with a device that captures the fob's signal — often reaching it through a wall, window or door.
- A second thief stands by the car with a device that re-broadcasts that signal to the vehicle.
- The car "sees" the key, unlocks and starts. They drive off.
The whole thing can take less than a minute, in near silence, at 3am. The first you know of it is an empty space on the drive.
Why alarms and factory immobilisers don't help
To the car, a relayed signal is indistinguishable from the real key. Every check the vehicle makes passes. The alarm isn't triggered because, as far as the car is concerned, the owner just unlocked it. The factory immobiliser is satisfied for the same reason. The attack doesn't break security — it impersonates it.
How you actually stop a relay attack
You stop it by adding a layer the relayed key can't satisfy. The most reliable is an immobiliser that is released by something other than the key — your phone.
IMMOSTOP holds the engine immobilised at two separate points and only releases them when your authorised phone is in range. A relayed or cloned key gets a thief into the car, perhaps — but the car won't drive for anyone but you. It arms and disarms automatically as you come and go, and runs in the background with the app closed.
Relay theft copies the signal. It can't copy your phone. See how IMMOSTOP stops it →
More on vehicle security
- How to protect your car from keyless theft
- Immobiliser vs tracker: which actually stops car theft?
- How IMMOSTOP works
- Compare IMMOSTOP vs trackers, steering locks & aftermarket immobilisers
- Order IMMOSTOP (£349 all-in, fitted)
- Car immobiliser fitting in your area
- Autosecureshop — vehicle security specialists