Relay Attack Car Theft: How Thieves Exploit Smart Keyless Entry

Overview

Keyless entry offers great convenience — the car unlocks and starts just by having the fob in your pocket, no button press needed. But that convenience opened the door to a new theft method known as a 'relay attack,' where thieves use two cheap electronic devices: one held close to the fob inside the house (even through a wall) to capture its signal, and another held near the car to relay that signal as if the real key were right beside it, unlocking and starting the car within seconds while the actual fob never leaves its spot. This crime is completely silent and leaves no visible sign of forced entry or damage.

Symptoms

• No mechanical symptoms on the car itself; the only sign is it physically disappearing from where it was parked
• Some victims notice the car was normally locked in the evening and gone by morning with no sign of force
• Home security cameras sometimes show two people approaching the house and car with small devices right before the theft
• Some modern smart fobs show an alert on the car's screen or mobile app when an unusual connection attempt is detected

Likely causes

• The smart fob being left near an exterior door or window, making it easy to capture its signal from outside
• Not using any signal-blocking barrier (like a Faraday pouch) while storing the fob at home
• Relatively older keyless entry systems lacking modern protections like time-of-flight signal measurement
• Leaving the car in dark or unmonitored areas, making it easier for thieves to approach unnoticed

Diagnosis & repair steps

1. Store the smart fob in a signal-blocking pouch or box (Faraday pouch) when not in use, especially at night
2. Keep the fob away from exterior doors and windows as much as possible
3. Enable 'Key Off / Sleep Mode' if your fob supports it via a specific button press
4. Use an additional steering wheel lock as a second, visually deterring layer even if thieves manage to open the door
5. Ask the dealer about a fob software update if the manufacturer has issued a security patch for your model

Expected cost

A signal-blocking Faraday pouch: $8-27, one of the cheapest and most effective protection measures. An additional steering lock: $27-80. A fob software update at the dealer if available: often free or for a nominal $15-40 fee. Compared to losing an entire car, these preventive costs are minimal.

Figures are a guidance range calculated with a published method — read the methodology.

How to prevent it

Invest in a Faraday pouch immediately if your car supports keyless entry, park in well-lit and monitored areas whenever possible, and periodically check with the dealer for fob security updates, especially for models reported as higher-risk for this theft type by insurance companies.

FAQ