How to Protect Your Car from Modern Relay Attacks

Keyless entry systems have made accessing our vehicles effortless, but this convenience has created a significant vulnerability known as the relay attack. In less than sixty seconds, thieves can use inexpensive technology to trick your car into unlocking and starting without ever touching your keys. This guide explains exactly how these attacks work and details specific, actionable steps you can take to secure your vehicle immediately.

Understanding the Relay Attack Mechanism

To protect your vehicle, you first need to understand the method thieves use. A relay attack usually involves two people working together.

  1. The Scanner: The first thief stands near your house or front door holding a device that scans for the signal emitted by your key fob.
  2. The Transmitter: The second thief stands next to your car holding a receiver.
  3. The Relay: The device near your house captures the weak signal from your key (which might be sitting on a hallway table) and amplifies it. It transmits this boosted signal to the second device next to the car.
  4. The Theft: The car detects the signal and believes the key is physically present. The doors unlock, and the push-to-start button becomes active. The thieves drive away without causing any physical damage to the vehicle.

This process exploits the “always-on” nature of standard keyless entry fobs. Fortunately, blocking this communication is often cheap and effective.

The Most Effective Defense: Faraday Bags

The simplest way to stop a relay attack is to block the signal your key emits when you are not using it. This is best achieved using a Faraday bag or pouch.

What is a Faraday Bag?

A Faraday bag is a pouch lined with metallic material that blocks electromagnetic fields. When you place your key fob inside and seal the velcro flap, the signal cannot pass through the material. If a thief tries to scan for your key, their device will find nothing.

Choosing the Right Product

Not all signal-blocking pouches are created equal. You need a product that blocks RFID, WiFi, Bluetooth, and NFC signals completely.

  • Ticonn: The Ticonn Faraday Bag is a popular choice that often comes in a two-pack. This is crucial because you must protect your spare key as well.
  • Mission Darkness: For higher durability, Mission Darkness offers forensic-grade shielding bags. These are more expensive but are designed to withstand heavy wear and tear without losing their shielding integrity.
  • Lanpard: Another reliable brand that offers key-sized pouches specifically designed for automotive security.

Usage Tip: Test your bag periodically. Put the key in the bag, stand next to your car, and try to open the door. If the door opens, the shielding has failed, and it is time to replace the pouch.

Physical Deterrents: The Second Line of Defense

If a thief manages to bypass the electronic security or if you forget to pouch your keys, physical barriers can save your car. Relay attacks are about speed and silence. Physical locks create noise and delay, which most thieves want to avoid.

Steering Wheel Locks

While they may seem old-fashioned, steering wheel locks are highly effective against modern high-tech theft.

  • The Club: The classic yellow bar is a strong visual deterrent. The “3000 Twin Hooks” model is harder to pry off than standard versions.
  • Disklok: For higher security, the Disklok encloses the entire steering wheel. Even if thieves cut the steering wheel rim, they cannot rotate the device to drive the car. It is heavy and cumbersome, but it provides the highest level of physical protection.

OBD Port Locks

Thieves sometimes use the On-Board Diagnostics (OBD) port to program a new key if they cannot relay the signal of the old one. This port is usually located under the dashboard on the driver’s side. An OBD port lock covers this plug with a metal cap, preventing unauthorized access to the car’s computer.

Advanced Electronic Solutions

For high-value vehicles, you might consider aftermarket electronic security that goes beyond the factory alarm.

Ghost Immobilizers

A “Ghost” immobilizer (such as the Autowatch Ghost II) connects to the vehicle’s CAN data network. Even if the thieves trick the keyless entry system and get the engine running, the car will not drive.

  • How it works: You must enter a unique PIN code using existing buttons in your car (like the volume up, cruise control, or window switches) before the gear will engage or the engine will fully start.
  • The Advantage: The device is silent and does not emit radio signals, making it impossible for thieves to find or disable it without dismantling the dashboard.

Motion Sensor Fobs (Sleeping Keys)

Check if your car manufacturer offers “sleeping” key fobs. Brands like Ford, Audi, BMW, and Mercedes-Benz have started including motion sensors in their newer fobs.

  • Function: If the key does not move for a set period (usually 40 seconds to 2 minutes), it enters sleep mode and stops transmitting a signal.
  • Upgrade: If you have an older model, contact your dealership. Some manufacturers sell upgraded fobs with this motion sensor technology that can be programmed to your existing vehicle.

No-Cost Behavioral Changes

You can reduce your risk immediately without spending money by changing how you handle your keys.

  1. Distance Matters: Do not leave your keys on a hook or table immediately next to your front door. This is the first place thieves scan. Move them to a drawer in the kitchen or a spot centrally located in the house, as far from exterior walls as possible.
  2. Disable Keyless Entry: Many fobs allow you to turn off the wireless transmission manually.
    • Toyota/Lexus: On many fobs, you can hold the ‘Lock’ button and press ‘Unlock’ twice. The LED will flash four times, indicating the key is deactivated. Pressing any button reactivates it.
    • Mercedes-Benz: Pressing the ‘Lock’ button twice in rapid succession often disables the Keyless-Go function.
    • Check your manual: Consult your owner’s manual to see if your specific fob has a battery-saving or deactivation mode.

Summary of Protection Strategy

To fully secure your vehicle, use a layered approach:

  • Layer 1: Keep keys in a Faraday bag (like Ticonn) away from the front door.
  • Layer 2: Use a visual deterrent like a steering wheel lock (The Club).
  • Layer 3: For high-risk vehicles, install a CAN-bus immobilizer (Ghost).

Frequently Asked Questions

Does wrapping my key in tin foil work? Wrapping a fob in aluminum foil can dampen the signal, but it is not a reliable long-term solution. It is difficult to get a perfect seal every time, and the foil degrades quickly with use. A dedicated Faraday pouch is safer and more durable.

Can I put my keys in the microwave or freezer? A microwave acts as a Faraday cage and will block the signal, but this is dangerous. If someone accidentally turns the microwave on with the keys inside, the battery will explode and destroy the fob and the appliance. Freezers may block signals, but the extreme cold can damage the battery life and the electronics within the fob. Avoid these methods.

Will my insurance cover a relay attack theft? Most comprehensive insurance policies cover theft, but disputes can arise. Since relay attacks leave no broken glass and the thief technically uses a “key,” some insurers may initially investigate for fraud. Proving you have a Faraday pouch or an immobilizer can demonstrate due diligence. Always check the specific wording of your policy regarding “keyless theft.”

How do I know if my car is at risk? If you have a push-to-start button and you can unlock the door by simply grabbing the handle while the key is in your pocket, your car is vulnerable to relay attacks. If you have to press a button on the fob to unlock the car, you are generally safe from this specific type of theft.