Keyless car theft: how the relay attack works and how to protect yourself

How thieves steal a keyless car

Thieves work in pairs. One gets as close to your key as possible, and the other stands by the car. Their devices relay the signal, so the car thinks the key is next to it.

This works because you unlock a keyless car by taking the handle while the key is in your pocket. The car then sends a question to the key, and the key answers. The car knows the key answered, but not how far away it is. More about what keyless is

1. The thief at the car takes hold of the handle, and the car sends a question to the key.
2. The device at the car passes the question to the second device, near your key.
3. The key answers, and the answer travels back the same way.
4. The car unlocks. The thief gets in, starts the engine and drives off.

A running car does not switch off when the signal is lost, because that would be dangerous while driving. Some cars only beep. So the thief can drive it far away.

Which cars are at risk

Almost every car that unlocks or starts without taking the key out is at risk. In a test of about 700 keyless cars, a signal relay device opened more than 90% of them. Some newer cars resist it, because their key measures how far away it really is.

If the car unlocks when you grab the handle while the key is in your pocket, you have keyless. The same applies if the car starts with a button, without putting the key in the ignition.

Where thieves catch the key signal

The thief only needs his device to be close to your key. The car can be further away: in a test, the signal was relayed to a car as far as 60 metres away.

• The key is at home, near a door or windowThe device picks up the key signal even through a wall, door and window. In a test, on some cars the device reached the key from as far as 6 to 8 metres. The key was on a table in the house, the device by the window, and the car in front of the house opened and started.
• The car is in a car park and you have walked awayThieves place a device by a spot everyone walks past, at a lift, a corridor or a pay machine. When you walk past it with the key in your pocket, the car unlocks, and the thief starts it and drives off.

!After the theft there are no signs of a break-in on the car. The car is opened with your key signal, so even a car that logs openings records that your key opened it.

How to protect yourself from keyless theft

A keyless car is best protected by an immobiliser and a key pouch together. The pouch keeps the key signal from the thief, and the immobiliser stops the engine from starting even when the thief does catch the signal.

• ImmobiliserThe engine starts only when the car has both the right key and your fob or code. You do not have to switch the immobiliser on, so it protects even when you forget the key outside the pouch. More about the immobiliser
• A pouch that blocks the signalA key in the pouch does not answer the car, so the thief has nothing to relay. Test the pouch on your own car, because not every one blocks. More about the key pouch
• An alarm with an engine lock and a fobThe engine will not start without the fob, even when a thief unlocks the car with your key's signal. The alarm should disarm only with the fob, even when you arm it with the factory key. More about alarm installation
• GPS trackingA message arrives as soon as someone moves the parked car, and you see where it is on your phone. More about GPS tracking

Also

• At home, keep the key away from the front door and windows. The further the key is from an outside wall, the harder it is for the thief to catch it.
• Switch keyless off, if your car allows it. On some cars this is done by pressing the lock button on the key twice quickly. The buttons on the key still work, and keyless comes back as soon as you press any of them. Your car manual says how it works on your car.
• Park in a locked garage when you can, and use a steering wheel lock on the street. The lock is visible through the glass and makes the theft much harder for the thief. More about mechanical protection

What you will hear, and what is true

• “The car is locked, it cannot be opened.”The thief unlocks it with your key signal, as if you had walked up to it.
• “I have a factory alarm.”The car unlocks with your key signal, so the alarm switches off just as when you unlock it. What stops the thief is an engine lock that asks for your fob.
• “My key goes to sleep by itself.”Some keys stop unlocking the car when they lie still, on some after 2 minutes. Until they go to sleep, theft is possible, and the key wakes up as soon as you move it.
• “I had the OBD port relocated, so the car is protected.”Keyless theft goes through your key's signal, not through the port, so neither relocation nor an OBD port lock stops it. A thief can also steal a keyless car with a new key made through the port, and then the pouch is no obstacle. That is why a keyless car needs both protection against keyless theft and OBD protection. More about OBD protection

If your keyless car is stolen

1. Call the police straight away, on 192.
2. If the car has GPS, give its location to the police straight away. Do not go after the car yourself.
3. Notify the insurer within 3 days of learning about the theft. The law requires it.
4. When you report the theft, you hand over all the keys you got with the car and the fobs of the alarm listed in the policy. If one is missing, the insurer treats the car as having been unlocked.

More about what to do when your car is stolen

Frequently asked questions