Keyless Entry Relay Theft: What It Is and How to Block It

Relay theft is when someone amplifies the signal from your key fob, sitting inside your house, to trick your car into thinking the key is right next to it. The fix is a Faraday pouch, full stop. You don’t need to understand the electronics to block it. You need a $10 to $20 signal-blocking pouch by the door where you drop your keys, and the whole problem goes away.

What relay theft is, in plain terms

Modern keyless entry fobs constantly broadcast a low-power signal so the car can sense when the key is nearby and unlock without you touching a button. That convenience is the weak point. A signal relay device can pick up your fob’s broadcast from inside your house, near a front door or window, and repeat it out to a car parked in the driveway, tricking the car into unlocking as if the key were sitting on the seat. We’re not going to walk through how the devices work or how the attack is carried out step by step. That’s not information this site publishes, and it’s not information you need to protect yourself. What matters is the fix, and the fix is simple enough that you can have it in place tonight.

This isn’t a rare or theoretical problem. Insurance industry data has flagged keyless car theft as a growing share of vehicle theft claims in areas with a lot of passive-entry vehicles, and it tends to cluster on newer models from manufacturers that pushed proximity unlocking as a standard feature. If your car came with a fob you never have to press, walk-up-and-unlock convenience, you’re a candidate for this problem. If your fob still requires a button press before the doors open, you can mostly skip this article.

The one tool that blocks it: Faraday pouches and boxes

A Faraday pouch is a lined bag that blocks radio signals from getting in or out. Drop your fob in one and it can’t broadcast, which means there’s nothing for a relay device to pick up in the first place. Brands like Mission Darkness and Silent Pocket make pouches built specifically for key fobs and phones, and either works fine as long as you use it every time you walk in the door. A pouch sitting empty in a drawer doesn’t help anyone.

How do you know a pouch is working?

A quick test: put your fob in the pouch, then walk up to the car and try the door handle the way you normally would with the fob in your pocket. If the door stays locked and the car doesn’t respond, the pouch is doing its job. Some people also test with a phone, since a pouch that blocks a phone’s signal (you’ll notice a dropped call or lost Wi-Fi the moment it goes in) is reliably blocking the weaker fob signal too. Worn or damaged pouches can lose their shielding over time, especially cheaper ones with thin lining, so a periodic re-test isn’t a bad habit if you’ve had the same pouch for a couple of years.

Does turning off keyless entry work?

Some cars let you disable the fob’s passive proximity broadcast through a menu setting, which closes the gap without buying anything. It’s a legitimate option if your model supports it, but it also means digging through a manual or a dealer visit to find the setting, and you lose the walk-up-and-unlock convenience you probably bought the car for in the first place. For most people, a pouch by the door is the lower-friction fix, and you don’t lose any functionality. You just add one habit.

A steering wheel lock is worth pairing with either approach, since it’s a visible deterrent that doesn’t depend on the fob at all. We rank it alongside other physical devices in our guide to car anti-theft devices that are worth buying.

Other habits that help

Park in a garage or under a light where you can, since relay theft still requires proximity to the car, and a thief working in the open under a streetlight is taking a bigger risk than one in a dark driveway. Keep the fob away from windows and exterior walls overnight, not just in a pouch but physically further from where a relay device would be aimed. A metal container, like a microwave or a metal tin with a tight lid, can work in a pinch as an improvised Faraday cage if you don’t have a pouch handy, though a purpose-built pouch is more reliable and doesn’t require remembering which drawer the tin is in. Neither of these habits replaces the pouch, they just shrink the odds further on nights when the routine slips.

Relay theft only threatens cars with passive keyless entry. If your car still uses a traditional key or a fob you have to press, none of this applies to you. For the theft risks that hit every car regardless of key type, see what stops catalytic converter theft.

Where this fits with the rest of your car security

A Faraday pouch is a prevention tool, and prevention only gets you so far on its own. If a theft happens anyway, recovery and evidence come from a different layer entirely. See GPS trackers vs dash cams for what each one catches after the fact. And if personal safety while you’re out and about matters as much as the car does, our guide to legal self-defense items covers what’s worth carrying alongside it.

None of these layers require much money or effort individually. The pouch is ten dollars, the habit costs nothing, and together they close off the specific weak point that passive keyless entry created. Most owners who’ve had a car targeted once never skip the pouch again, which tells you most of what you need to know about how well it works.

Frequently asked questions