You're asleep. Your car is parked in the driveway. Your key fob is sitting on the hallway table near the front door.
Two people walk up to your house. One holds a device near your door. The other stands by your car with a second device. In under 30 seconds, your car unlocks. The engine starts. They drive away.
No broken windows. No alarm. No forced entry.
This is a relay attack — and it's one of the fastest-growing methods of car theft worldwide.
How Relay Attacks Work
Modern smart key fobs constantly broadcast a low-power radio signal. When you walk up to your car with the fob in your pocket, the car detects this signal and unlocks automatically. Press the start button, and the car verifies the fob is inside before starting the engine.
The system was designed for convenience. But thieves figured out how to exploit it.
Here's what happens during a relay attack:
- Thief A stands near your house with a signal amplifier — close enough to pick up your fob's signal through the wall
- The amplifier captures the fob's signal and relays it to a second device
- Thief B stands next to your car holding the second device, which rebroadcasts the signal
- Your car thinks the real fob is right there. It unlocks and starts
The entire process takes 10 to 60 seconds. The devices cost as little as $100 online.
The key fob isn't "cloned" in the traditional sense — the thieves are just extending its range in real time. But the result is the same: they drive away in your car.
Which Cars Are Vulnerable?
Any vehicle with a passive keyless entry system (where the car unlocks when you approach without pressing a button) is potentially vulnerable. This includes most cars manufactured after 2015 with smart key technology.
Higher Risk:
- Luxury vehicles — often targeted due to resale value
- SUVs and trucks — popular targets, especially Toyota Highlanders, Honda CR-Vs, Dodge RAMs
- Cars with basic smart key systems — early implementations have weaker encryption
- Vehicles parked in driveways — more accessible than garage-parked cars
Lower Risk:
- Cars with UWB (Ultra-Wideband) keys — newer technology that measures exact distance and can't be relayed
- Vehicles with motion-sensor fobs — the fob stops broadcasting when stationary
- Cars parked in garages — the signal is harder to capture through multiple walls
Some manufacturers have started addressing this. BMW, Audi, and Mercedes have introduced motion-sensor fobs in recent models. Apple's UWB technology used in some newer vehicles is designed to be relay-proof.
But the vast majority of cars on the road today don't have these protections.
How to Protect Yourself
The good news: protecting yourself is simple and cheap.
1. Use a Faraday Pouch ($8 – $15)
A Faraday pouch (or bag) blocks all radio signals from leaving or reaching your key fob. When your fob is inside the pouch, it can't be detected by a relay device.
How to use it:
- Drop your fob in the pouch every time you're at home
- Make sure the pouch is fully closed — even a small gap lets signal through
- Test it: put the fob in the pouch and try to unlock your car. If it doesn't unlock, the pouch works
Look for pouches specifically rated for RFID and key fob signal blocking. Not all "signal blocking" products actually work — test before you trust.
2. Store Your Fob Away From Doors and Windows
If you don't have a Faraday pouch, distance helps. The relay device needs to be close enough to pick up your fob's signal (usually within 10-15 feet through walls).
- Don't leave your fob on the hallway table near the front door — this is the #1 mistake
- Store it in a central room or upstairs, as far from exterior walls as possible
- A metal container (like a tin or metal box) provides some signal shielding, though it's less reliable than a proper Faraday pouch
3. Disable Passive Entry (If Your Car Allows It)
Some vehicles let you turn off the passive keyless entry feature through the settings menu. You'll need to press the button to unlock instead of just walking up to the car.
Check your owner's manual or search your car's settings for:
- "Passive entry" or "keyless access"
- "Approach unlock" or "walk-up unlock"
- "Smart key settings"
This disables the convenience feature but eliminates the relay attack vector entirely.
4. Use a Steering Wheel Lock ($25 – $50)
Old school? Yes. Effective? Absolutely. Relay attacks get thieves into the car and start the engine, but a visible steering wheel lock adds a physical barrier that most thieves won't bother with. They'll move on to an easier target.
5. Check Your Car's Vulnerability
Not sure if your specific vehicle is at risk? FobHunt's VIN report includes a theft risk assessment for your exact make, model, and year — including whether your smart key system is vulnerable to relay attacks and what protection we recommend.
Check your car's theft risk at FobHunt
What About Signal-Blocking Phone Cases?
Some people keep their fob in a signal-blocking phone case. These can work, but they're hit-or-miss. Many aren't fully shielded and still leak enough signal for a relay device to detect.
If you go this route, always test it with your car before trusting it. Put the fob in the case, hold it next to your car, and see if the car still detects it.
The Bigger Picture
Relay attacks aren't a hypothetical threat. Police departments across the US, UK, and Europe have reported significant increases in keyless car theft over the past five years.
The auto industry is slowly catching up. Ultra-Wideband technology, motion-sensor fobs, and improved encryption are making their way into newer vehicles. But if your car was built between 2015 and 2023 with a passive keyless system, you're likely vulnerable right now.
The fix is simple: a $10 Faraday pouch and the habit of using it. That's all it takes to make your car a much harder target.
Want to know your car's specific risk level? Enter your VIN at FobHunt for a complete theft risk assessment including relay attack vulnerability, protection recommendations, and more.
Image Prompts for ChatGPT/DALL-E:
Featured Image: "Dark moody photograph of a car key fob on a nightstand near a front door at night, with subtle glowing concentric radio wave circles emanating from it, cinematic lighting, modern home interior, security concept"
Optional In-Article Images:
- "Simple infographic-style illustration showing two figures: one near a house with a relay device capturing a key fob signal, the other near a car receiving the relayed signal, dark background, clean minimalist style with orange accent lines"
- "Product photograph of a black Faraday pouch with a car key fob partially visible inside it, clean dark surface, studio lighting, straight-on angle"
- "Photograph of a car dashboard at night showing the push-to-start button glowing, from driver perspective, moody cinematic lighting"