Keyless Car Theft: How to Protect Your Keys

Where to keep your car keys at night, whether Faraday pouches and foil actually work, and what genuinely reduces the risk of keyless car theft.

Keep your keys away from exterior walls, windows and the front door — the closer they sit to the outside of the house, the easier they are to reach electronically. A signal-blocking pouch or box adds a reliable second layer. Never leave a fob in the car overnight, and never hide a spare on the vehicle.

That’s the practical answer. The rest of this page is why, and which of the things you’ve read about actually work.

What relay theft actually is

If your car unlocks as you approach and starts with a button, the key is transmitting. That’s the feature. It’s also the exposure.

Relay theft works by extending the conversation between your key and your car further than it was designed to reach — so the car believes the key is next to it when the key is actually inside your house. The car does exactly what it was built to do, for the wrong reason.

We’re not going to describe how it’s done, and no reputable locksmith will. What matters to you is the shape of it: the attack targets the key, not the car. That’s why every effective defence is about the key.

Two things worth knowing.

Keyless entry did not make cars easy to steal in general. Immobilizers made theft substantially harder than it was in the 1990s, and that’s still true — our page on how car immobilizers work covers that. Relay theft is a specific technique against a specific convenience feature.

And once a car has been started this way it generally keeps running until it’s switched off, because the check happens at start rather than continuously. Which is why a vehicle can end up a long way from where it was taken.

Do Faraday pouches and boxes work?

Yes, in principle, and this is the one product category worth owning.

The idea is old and well understood: a conductive enclosure blocks radio signals from getting in or out. A pouch or box lined with conductive fabric or metal mesh does that for a key fob. If the key can’t be reached, it can’t be relayed.

Three caveats worth having.

The seal matters more than the product. A pouch left half-open protects nothing. Whatever you buy has to close completely, every time, which in practice means it has to be convenient enough that you’ll actually do it.

They degrade. Fabric pouches wear at the fold and the lining cracks with use. Test yours occasionally — put the key in, close it, and try to unlock the car standing next to it. If the car responds, the pouch is finished.

Battery drain is an open question. It’s one of the most common things people ask, and the honest answer is that we don’t know definitively. Some owners report faster drain, and the plausible mechanism is the fob repeatedly searching for a signal it can’t find. Others report no difference. If your fob battery seems to be going quickly, it’s a reasonable thing to consider — our page on key fob batteries covers the symptoms.

We’re not going to recommend a brand. We haven’t tested them, and the pages that do rank for this are mostly affiliate content. Buy one that closes properly and test it yourself.

Foil, tins, and the fridge

Three folk remedies, and they’re asked about constantly.

Foil. The physics isn’t wrong — aluminium is conductive and will block a signal if the key is fully and tightly wrapped with no gaps. The problem is doing that reliably every night. A loosely wrapped fob with a seam is not protected, and you can’t tell by looking. It’s a workable emergency measure and a poor system.

A metal tin. Better than foil in principle because it’s a rigid enclosure. Whether it works depends entirely on the seal — a biscuit tin with a loose lid may leak, and again you can’t tell without testing. If you use one, test it the same way: key inside, lid on, stand next to the car.

The fridge. This is the one everyone asks about, and there’s a real reason behind it. A fridge is a sealed metal box, so it’s an accidental Faraday cage. It does often work.

It’s still a bad idea. Condensation and electronics don’t mix, and a fob that’s been through a few hundred cold cycles is a fob you’ll be replacing early. You’ve solved a theft problem by creating a moisture problem. Use a pouch.

Where thieves look

Two different threats, and they call for the same answer.

Electronic reach is about distance. A key on a hall table three feet from the front door is far easier to reach than one in a back bedroom. Every extra wall and every extra metre helps.

Physical searching is more mundane. Keys get taken from hooks by the door, from hall tables, from kitchen counters near a window, and through letterboxes with a hooked implement. The obvious places are obvious to everybody.

The overlap is convenient: the safest spot is deep inside the house, away from external walls and doors, and not visible from a window. That answers both problems at once.

Where not to put a spare

Not on the car. Magnetic key boxes under the wheel arch or behind the bumper are known to everyone who might look, and a spare on the vehicle means the vehicle has its own key attached to it. Any protection you’ve arranged indoors is irrelevant if the second key is outside.

Not in the car overnight. Including the glovebox, and including “just this once.” A fob in the car is a fob within reach.

Not in a coat by the door. It’s the first place searched and it’s usually the closest point to the street.

Not under the mat, in a plant pot, or on the door frame. These aren’t hiding places, they’re a short list.

If you need to leave a key for someone, a key safe fitted to the wall with a combination is the reasonable option — and if it’s a car key, consider whether it needs to be the working one.

What else actually helps

A steering lock. Genuinely worth mentioning because no electronic attack does anything about it. It’s visible, it takes time to defeat, and time is what a thief doesn’t have. Low-tech and unfashionable, and it still works.

Check whether your car can turn the feature off. Some vehicles let you disable passive entry, or have a motion-sensing fob that stops transmitting when it’s been still for a few minutes. Worth looking in the manual.

Park thoughtfully. Off-street where possible, under a light, nose-in so the front of the car is harder to reach.

Keep the spare somewhere different. Not next to the primary. If a thief finds one drawer, they shouldn’t find both.

Frequently asked questions

Where should I keep my car keys at night?

Away from exterior walls, windows and the front door — deep in the house rather than near the street. A signal-blocking pouch or box adds a second layer that works regardless of position.

Do Faraday boxes for car keys work?

Yes, when properly sealed. A conductive enclosure prevents the key being read. The failure mode is almost always a pouch left partly open or one that's worn out, so test yours occasionally.

Do RFID blockers work for car keys?

The same principle applies — anything that fully encloses the key in a conductive layer prevents it transmitting. What matters is the seal and whether you use it consistently.

Does wrapping a key fob in foil work?

It can, if the fob is completely and tightly wrapped with no gaps. Doing that reliably every night is the problem. Fine as an emergency measure, poor as a routine.

Why do people put their car keys in the fridge?

A fridge is a sealed metal box, so it blocks the signal by accident. It often works and it's still a bad idea — condensation will shorten the life of the fob.

Do Faraday pouches drain the battery?

Commonly asked and not clearly settled. Some owners report faster drain, with the plausible explanation being the fob searching for a signal it can't find. Others notice nothing.

Which Faraday key fob protector is best?

We don't recommend a brand — we haven't tested them, and most pages that do are affiliate content. Choose one that closes completely and test it yourself against your own car.

Is it bad to leave a key fob in the car overnight?

Yes. A key inside the vehicle is within reach of anyone at the vehicle, and it defeats whatever precautions you've taken indoors.