Relay Attacks: How Keyless Cars Get Stolen, and How to Stop It
Keyless entry made life easier and gave thieves a new opening. The relay attack is the technique behind a wave of keyless car thefts, and it unsettles owners precisely because it leaves no broken glass and no forced lock - the car simply opens and drives away. The reassuring part is that the defence is cheap, simple and almost completely effective.
This guide explains, without a how-to, what a relay attack is and why it works, which cars are vulnerable, and the handful of inexpensive steps that shut it down - so the convenience of keyless entry need not be a liability.
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Get my quotesWhat keyless entry actually does
A keyless car constantly listens for its fob. When the fob is close, the car unlocks and allows starting; when it is far, it stays locked. The convenience is that the key never leaves your pocket.
The vulnerability lives in that constant listening: the car decides the fob is near based on a signal, and a signal can be relayed.
What a relay attack is, in plain terms
A relay attack works by extending the apparent reach of your fob - making the car believe the key is right beside it when it is actually inside your house. The car, fooled into thinking the fob is present, unlocks and starts.
That is the concept, and it is as far as this guide goes - the value to an owner is in the defence, not the method.
Why it leaves no trace
Because a relay attack uses the car's own legitimate unlocking process, there is no broken window, no forced lock, no alarm. To anyone watching, the thief simply opens the door and drives off as though they own it.
This traceless quality is what makes it unnerving and what makes physical and tracking defences, which do not rely on a break-in being detected, so important.
Which cars are vulnerable
Any car with keyless entry and keyless start - the kind where you never press a button to unlock or insert a key to start - is potentially exposed. This now spans a huge range of models, not just premium ones.
If your car unlocks as you approach and starts with a button while the fob sits in your pocket, this guide applies to you.
The fob pouch: the complete defence
The single most effective answer is a signal-blocking pouch - a small lined sleeve that stops the fob transmitting while inside it. With the fob blocked, there is no signal to relay, and the attack simply fails.
They cost very little, work completely, and need only one habit: putting the fob in the pouch when you get home.
Where you keep the fob at home
Relay attacks are usually mounted from outside your home, reaching a fob left near the front door. Keeping the fob well inside the house, away from external walls and doors, raises the difficulty even without a pouch.
Combine distance with a pouch and the attack has nothing to work with.
Disabling the fob's signal where possible
Some fobs can be put into a sleep mode that stops them transmitting until pressed - check your owner's manual, as it varies by manufacturer. Where available, it is a free, built-in version of the pouch.
Not every fob offers it, which is why the pouch remains the universal recommendation.
Physical deterrents still matter
Even if a relay attack opens the car, a steering lock, gear lock or wheel clamp still has to be dealt with - reintroducing the time and noise the attack was meant to avoid.
A relay attack defeated at the fob never gets this far, but a visible mechanical lock is a sound second line.
The role of an added immobiliser
An aftermarket immobiliser that requires a separate action or code to allow the car to start adds a layer the relayed signal cannot satisfy. Even with the doors fooled open, the car will not drive.
Paired with a tracker, it shifts a relay attempt from a clean theft to a stalled, traceable one.
How tracking backs it all up
If a relay attack does succeed, a tracker is what turns a silent disappearance into a recovery. The car may have left without a trace at the scene, but it cannot hide from a unit reporting its position.
This is the safety net under every electronic-theft defence: prevention at the fob, recovery through the tracker.
Signs your car may have been targeted
Relay attacks are quiet, but clues exist - a car found unlocked you are sure you locked, belongings disturbed, or a near-miss where the car was opened but a physical lock stopped the drive-off.
Any of these is a prompt to tighten the fob habits immediately, because a crew that probed once may return.
How worried you should actually be
It is worth keeping relay attacks in proportion. They are real and they happen, but they require equipment and proximity to your fob, which means they concentrate on cars worth the effort and homes where the fob sits conveniently near the door. A fob pouch removes you from that pool almost entirely.
So the honest answer is: aware, not anxious. This is a threat with a near-complete, almost free defence, which puts it in a very different category from risks you can only partly mitigate. Take the simple step and the worry can genuinely be set down.
The keyless convenience is worth keeping
Some owners ask whether they should disable keyless entry altogether. For most, that is an overcorrection - it trades a convenience you use daily for protection a pouch already provides. The technology is not the problem; an unprotected fob near an external wall is.
Keep the convenience, add the pouch, mind where the fob lives at home, and back it with a tracker. That combination preserves what made keyless entry pleasant while closing the door it opened, which is a better outcome than giving up the feature entirely.
The complete relay defence, summarised
Pouch the fob at home, keep it away from external walls, use sleep mode if your fob has it, add a visible physical lock and ideally an immobiliser, and run a tracker as the recovery backstop.
Done together, these reduce relay-attack risk to near zero for a tiny outlay - the rare case of a serious threat with a genuinely simple answer.
Frequently asked questions
What is a relay attack?
It is a technique that extends the apparent reach of your keyless fob, making the car believe the key is right beside it when it is actually inside your house. The car unlocks and starts as normal - with no broken glass or forced lock, because it uses the car's own legitimate process.
Which cars are vulnerable to relay attacks?
Any car with keyless entry and keyless start - where you never press a button to unlock or insert a key to start - is potentially exposed, across a huge range of models, not just premium ones. If your car unlocks as you approach and starts with a button, this applies to you.
How do I stop a relay attack?
A signal-blocking fob pouch is the complete answer - it stops the fob transmitting, so there is no signal to relay and the attack fails. It costs very little and needs only one habit: pouching the fob when you get home. Keep it away from external walls too.
Why don't relay attacks set off the alarm?
Because they use the car's own legitimate unlocking process - there is no break-in to detect, so no alarm, no broken window, no forced lock. This is exactly why fob and tracking defences, which do not rely on a break-in being noticed, matter so much.
Does an immobiliser help against relay attacks?
Yes - an aftermarket immobiliser requiring a separate action or code adds a layer the relayed signal cannot satisfy, so even with the doors fooled open the car will not drive. Paired with a tracker it turns a relay attempt into a stalled, traceable one.
Can my fob be disabled when not in use?
Some fobs have a sleep mode that stops them transmitting until pressed - check your owner's manual, as it varies by manufacturer. Where available it is a free, built-in version of the pouch, but since not every fob offers it, the pouch remains the universal recommendation.
What if a relay attack still succeeds?
A tracker turns a silent disappearance into a recovery - the car may leave without a trace at the scene, but it cannot hide from a unit reporting its position. That is the safety net under every electronic-theft defence: prevention at the fob, recovery through the tracker.
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