How to Protect a Keyless Car from Relay Theft
Relay theft works by extending the signal from a key inside your house to a car outside it. No code is broken and no lock is forced, which is why it leaves no sign. The measures that genuinely help are about distance and shielding: keep the fob away from external walls and doors, store it in a signal-blocking pouch, and find out whether your fob has a motion-sensing sleep mode.
What relay theft actually is
A keyless entry system works by the car continuously listening for its key. When the fob is close enough, the car unlocks and allows itself to be started. The convenience is the whole point, and so is the vulnerability.
A relay attack uses two devices and usually two people. One stands near your house and picks up the low-power signal your fob is broadcasting from wherever it is inside. That signal is relayed to a second device standing next to the car, which rebroadcasts it. As far as the vehicle is concerned, the key is present.
It is worth being clear about what this is not. Nothing is hacked, no encryption is defeated and no lock is damaged. The car behaves exactly as designed, having been told something untrue about where the key is. That is also why there is frequently no physical evidence afterwards, which can complicate an insurance claim.
Which cars are affected
Any vehicle with keyless entry and push-button start is potentially exposed, across essentially all manufacturers. It is not a premium-badge problem, although higher-value cars attract more attention.
A traditional key that you physically insert and turn, or a remote fob where you press a button to unlock, is not vulnerable to this specific attack, because the key only transmits when you tell it to. Those vehicles have their own risks, but relay theft is not one of them.
If you are not sure which type you have, the test is simple: if the car unlocks when you approach with the key in your pocket and starts without the key going anywhere, it is a keyless system.
The measures that genuinely reduce risk
These are ordered roughly by how much difference they make relative to the effort involved. None of them require buying anything expensive.
- Move the fob away from the front of the house. Distance is the single most useful variable, because the relay has to pick up the signal in the first place. A key on a hall table by the front door is the worst case; a key in a back room is materially better.
- Use a signal-blocking pouch or box, and test it. Lock the car, put the fob in the pouch, and see whether the car still responds when you stand next to it. Pouches wear out and linings fail, so this is worth repeating occasionally.
- Do not leave the spare key somewhere convenient. A spare in a hallway drawer defeats every precaution taken with the main one. Store it properly or store it somewhere else entirely.
- Find out whether your fob has a motion-sensing sleep mode. Many manufacturers now fit fobs that stop transmitting after a period without movement, which removes the attack while the key is at rest overnight. On some vehicles this is enabled by default; on others it has to be switched on.
- Add a visible physical deterrent. A steering lock, a driveway post or simply parking another vehicle behind the first all add time and visibility, which is what opportunistic theft avoids.
- Park defensively where you can. A car on a driveway close to the house is the easiest configuration for a relay attack; a car in a garage is the hardest.
Things that sound sensible but are not
A few pieces of widely repeated advice are worth correcting, because acting on them can cause problems of their own.
- Putting the fob in a metal tin or the microwave
- The shielding is unreliable and untested, and people forget and switch the microwave on. Use a purpose-made pouch.
- Removing the fob battery each night
- It works, but the wear on the battery compartment and contacts causes its own failures over time, and it is the sort of routine that gets abandoned after a fortnight.
- Wrapping the key in foil
- Inconsistent, and it degrades quickly with handling. It is a demonstration, not a security measure.
- Assuming a factory alarm is enough
- The vehicle believes the key is present, so from its point of view nothing is wrong. The alarm has no reason to sound.
- Assuming it will not happen on a quiet street
- Relay equipment is portable and the attack is quick and quiet. Location helps far less than distance and shielding do.
If your keys are stolen rather than lost
This is a different situation from a mislaid key and needs a different response. A stolen key may be with someone who also knows where the vehicle is, particularly if it was taken with a bag containing an address, a parking permit or a driving licence.
Where the vehicle’s system supports it, keys can be re-learned so the missing ones no longer start the car. That is the step that resolves the risk, rather than simply having a replacement cut. Say clearly that the keys were stolen rather than lost, because it changes the correct approach.
Be aware that on some vehicles this requires every key to be present and re-learned together, which erases any key not physically there. If that applies to yours, bring every key you still own to the appointment. Report the theft to the police and to your insurer as well.
What to check on your own vehicle
Rather than general advice, these are the specific questions worth answering about the car on your drive. Autobahn can confirm the answers from your registration.
- Does the vehicle use keyless entry and push-button start, or a conventional remote?
- Does the fob have a motion-sensing sleep mode, and if so is it currently enabled?
- How many keys exist, and do all of them still work? An untested spare is not a spare.
- Where is each key kept overnight, and how close is that to an external wall or door?
- If the worst happened, does this vehicle support deleting a missing key from its memory?
Beyond the key: layers worth adding
- A tracker will not stop a theft, but it improves the chance of recovery. If the vehicle already has one, check the subscription is current and that you know how to report a theft through it.
- Manufacturer apps can alert you when a vehicle is unlocked or moved. Worth switching on if your vehicle supports it.
- Some vehicles allow keyless entry to be turned off, leaving button unlocking only. If you rarely use the keyless function, it removes the relay risk entirely.
- On some vehicles thieves use the diagnostic port to programme a key once inside. A physical lock over the port adds delay at exactly that stage.
- An aftermarket immobiliser adds a second authorisation the relay attack does not defeat. Have one fitted by a qualified installer and tell your insurer.
Keyless security questions
Does a signal-blocking pouch really work?
A good one does, and it is the most practical measure available. The important part is testing it rather than trusting it: put the fob inside, close it properly, and check whether the car still responds when you stand beside it.
They do degrade. Linings crease and tear with daily use, so retest occasionally rather than assuming a pouch bought two years ago is still doing its job.
Can you disable keyless entry on my car?
On some vehicles there is a manufacturer option to turn keyless entry off, or to enable a sleep mode on the fob, and on others there is not. It depends on the make, model and year.
Send the registration and we will tell you what your specific vehicle supports rather than guessing from the model name.
My car was stolen without the keys. How?
Relay theft is the most common explanation for a keyless vehicle taken with no sign of forced entry and no missing key. The car was told the key was present when it was not.
Tell your insurer and the police exactly that, because the absence of damage is otherwise easy to misread. If the vehicle is recovered, have the key situation reviewed before driving it again.
Is an older car with a normal key safer?
Safer from this specific attack, yes, because the key only transmits when you press a button. It is not safer in general — older vehicles have their own weaknesses, including simpler immobilisers.
The right precautions differ by vehicle age rather than one type being universally better.
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Want to know what your vehicle’s system actually does?
Send the registration. We will tell you which key system your car uses, whether it supports a fob sleep mode, and whether missing keys can be deleted.