Relay Attacks Explained: How Car Thieves Clone Your Key Fob
Your car was in the driveway at midnight. By morning it was gone.
No broken glass. No smashed lock. No alarm. Just an empty spot where it sat.
Here is the direct answer: most keyless cars are stolen with a relay attack. Two thieves, two small devices. One captures your key fob's signal through the wall of your house, the other relays it to your car, and the car unlocks and starts as if the key were sitting in the ignition. They do not really clone your key. They borrow its signal in real time. The whole thing takes under a minute and makes almost no noise.
Once you see how it works, the fix is obvious. So let's break it down.
What Is a Relay Attack?
A relay attack is a way to steal a keyless car by extending the range of its key fob.
Your fob and your car are built to trust each other when they are close. A relay attack tricks the car into thinking the fob is right there, when it is actually still inside your house. No hacking, no code-breaking. Just two devices passing a signal between them.
It is not the same as making a copy of your key. The real key never leaves your kitchen counter.
How a Relay Attack Works, Step by Step
The method is simple, which is exactly why it spread:
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Your fob is always talking. Even in a drawer, it sends out a short-range signal looking for your car.
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Thief A gets close to your house with a relay device that picks up that signal through a wall or window.
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The device passes the signal to Thief B, who is standing next to your car with a second relay device.
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The car hears its own key and does what it is designed to do. It unlocks, and it starts.
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They drive away. Your fob never moved. The car simply believed it was near.
That is the entire attack. No force, no noise, no trace on the driveway.
Why Keyless Cars Are So Easy to Take
The vulnerability is baked into the convenience.
Keyless entry works on proximity. The car unlocks when the key is near and starts when the key is inside. To make that seamless, the fob broadcasts constantly, and the car trusts whatever answers. A relay attack does not break that system. It uses it exactly as designed, just from farther away than the carmaker assumed.
In other words, the feature that lets you keep the key in your pocket is the same feature thieves lean on. The signal is always on, and being close is the only proof the car asks for.
Relay, Cloning, and Code Grabbing Are Not the Same
The word "clone" gets used loosely, so here is the honest version.
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Relay attack: the common one. Thieves extend your fob's live signal. Nothing is copied. This is what steals most keyless cars.
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Code grabbing: a separate technique that tries to capture and reuse the codes a fob sends. Modern rolling-code systems make this harder, but tools built to defeat them exist.
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True cloning: actually duplicating a key. This is rarer and harder than the headlines suggest.
Why does the distinction matter? Because it points straight at the fix. If the threat is your fob's signal being reached and relayed, then the answer is simple: stop the signal from being reachable at all.
How to Shut It Down
You cannot patch this with a car setting, because the fob has no off switch. So you take the signal off the table yourself.
A Faraday pouch is lined with conductive material that blocks every wireless signal in or out. Drop your fob inside and it goes silent. With no signal escaping, there is nothing for a relay device to catch, and the attack has nothing to work with. Not software. Not a gadget that needs charging. A physical barrier.
SLNT gear is protected by patented Silent Pocket technology and independently tested against military shielding standards, the same shielding trusted by military units and hundreds of thousands of everyday users.
A few honest limits, because precision beats hype. A pouch stops signal-based theft. It does not stop towing, glass-breaking, or wired attacks, so locks, cameras, and smart parking still matter. It also only works when the fob is actually inside, so make it a habit.
SLNT also lines bags and sleeves to block signals for phones and cards. One straight fact there: a Faraday sleeve stops signals from leaving your phone, but it does not turn off the microphone, since the mic is built into the device. The phone can still hear. Nothing it hears can transmit out of the bag.
Where This Fits Into Everyday Life
This is not about living on edge. It is about closing the easiest door in your driveway.
At home, aFaraday key fob pouch by the entryway turns off the overnight broadcast that relay thieves rely on. That single habit removes the most common theft window.
Protect the spare too. A shielded main key and an unprotected backup in a drawer still leaves an opening, so a secondFaraday sleeve for the spare closes it. Traveling or renting, a pouch keeps an unfamiliar fob quiet between trips out. Handing keys to a teen driver or a valet? Each set can go in its own pouch, so the signal is never sitting exposed.
None of this changes how you drive. It just decides when your key is allowed to speak.
Why It Matters
A car is a large thing to lose to a trick that takes less than a minute.
Relay theft works because it is quiet, fast, and invisible. The fix is just as simple, and it puts the decision back with you. You choose when your key can be reached and when it goes dark. That is real control, not a nightly hope that no one parks a relay box outside your house.
It buys back something practical too. No checking the driveway at 2 a.m. Just a quiet key and a car that stays where you left it.
Take the Signal Off the Table
Thieves count on your fob broadcasting around the clock. Take that away and their easiest move disappears.
A Faraday pouch does one job and does it completely. Sealed inside, your key goes silent, and there is no signal to relay.
If you want gear tested to actually shut the signal down, take a look at how SLNT pouches fit into your everyday carry. No urgency, no pitch. Just control.