Keyless Car Theft: How Relay Attacks Work

If you can walk up to your car and pull the door handle without pressing anything on the fob, and start the engine with a button while the fob stays in your pocket, your vehicle uses passive keyless entry. It is sometimes called "comfort access" or "smart entry".

A standard remote fob that needs a button press to unlock, and a physical key turned in the ignition to start, is not vulnerable to relay theft in the same way.

If you are unsure, check your handbook or ask your dealer. Some models offer keyless entry as an option, so two otherwise identical cars can behave differently. Keyless entry is one part of the wider picture in our complete UK car theft guide.

The fob's signal is designed to pass through pockets, bags and clothing for convenience. It also passes through doors, windows and walls. A key on a hallway hook or a console table near the front door is close enough to the car and the exterior for a receiver placed outside to pick up the signal.

The further inside the home the key is kept, and the more it is shielded, the harder a relay attack becomes. Distance and shielding both reduce the signal an attacker can capture. For the scale of the problem, see the latest UK car theft statistics.

A Faraday, or signal-blocking, pouch lines a small sleeve with conductive material that blocks radio waves. With the fob inside and the pouch closed, the car should not detect the key.

Quality varies. A worn seam, a damaged lining, or a pouch that is not fully closed will leak signal. Use a pouch for the main key and the spare — a spare left in a kitchen drawer is a common oversight.

A pouch is a useful layer, not a guarantee. Combine it with a physical lock and, where relevant, a tracker.

Many fobs can switch their wireless signal off when not in use. The method varies by manufacturer — often a double press of a button, a long hold, or a small switch inside the key casing. When the signal is off, the fob behaves like a traditional key until it is reactivated.

Check your vehicle handbook or ask your dealer for the exact sequence for your model. Some models revert the setting if the battery is changed, so re-test after a battery swap.

Police-backed advice is to keep keys and spares away from the vehicle, doors and windows. A position well inside the home — in a signal-blocking pouch, in a drawer or cupboard away from the entrance — reduces the signal an attacker can reach.

Avoid hallway hooks, console tables by the door, and anywhere visible from a window or reachable through a letterbox.

A relay attack defeats the electronic lock. A visible physical barrier — a tested steering-wheel lock, a wheel clamp, or pedal protection — is a separate obstacle that takes time and noise to remove.

Thieves often move on to an easier target when a physical lock adds minutes to the job. Look for locks that have been independently tested rather than the cheapest option. Physical locks are one layer in broader layered car-theft prevention.

Once inside, some thieves use the OBD port to program a new key. A physical OBD port protector locks over the connector and slows that attack. Relocating or hiding the port is a further option on some vehicles.

OBD protection is a useful layer for vehicles known to be targeted this way, but it is not a substitute for stopping the relay attack in the first place. If you are considering a tracker, our car tracker buyer's guide covers the options.

Some manufacturers release software updates that change keyless behaviour or patch known vulnerabilities — for example reducing the fob's signal interval or requiring a movement check before start. Check for recalls and software campaigns through your dealer or the manufacturer's owner portal.

A separate but related risk: a signal jammer can block the lock command from your fob. You press the button, walk away, and the car stays open. Always physically check a door handle has locked before leaving the vehicle.