Keyless entry cars are vulnerable to relay theft — a two-person attack where thieves amplify your fob's signal from inside your home to unlock and start your car in under 60 seconds. The single most effective countermeasure is a Faraday pouch ($10), which blocks your fob's signal completely while stored at home. Layer it with a steering lock or GPS tracker for maximum protection.
How Relay Theft Works — Step by Step
Thief 1 approaches your front door
Armed with a relay amplifier unit, they hold it against your exterior wall, door, or window — wherever your key fob is most likely to be (hall table, kitchen counter). The device scans for the fob's 315MHz or 433MHz signal through the wall.
Thief 2 stands next to your car
The second thief holds a relay receiver unit next to your car's door handle. The two devices wirelessly extend the communication between your car and your fob across 20–30 metres.
The car unlocks and starts
The car detects what it believes is the authorised fob and unlocks the doors. With the relay device still active and the fob signal being relayed, many vehicles will also start — the immobiliser is fooled because the car "sees" the fob's signal.
The car is driven away in under 60 seconds
The entire attack — from first scan to driving away — takes 20–60 seconds. There is no glass breaking, no alarm, and no obvious sign anything happened until you check your driveway the next morning.
Countermeasures — Ranked by Effectiveness and Cost
| Measure | Stops Relay Theft? | Cost | Effort |
|---|---|---|---|
| Faraday pouch for key fob | ✔ Yes — completely | $8–$15 | Minimal — use nightly |
| Disable keyless entry (car settings) | ✔ Yes | Free | Low — use physical button |
| Steering/pedal lock | ❌ Not directly | $30–$80 | Medium — fit/remove daily |
| GPS tracker | ❌ Not directly | $80–$150 + subscription | Low — passive |
| PIN to Drive (Tesla, some BMW/Volvo) | ✔ Yes | Free (software feature) | Minimal — enter PIN each time |
| Signal-blocking box (in-home safe) | ✔ Yes | $20–$50 | Low — stored at home |
| After-market OBD security device | ✔ Yes (prevents start) | $100–$250 installed | None after install |
Faraday Pouches — Your First Line of Defence
A Faraday pouch is a signal-blocking bag lined with conductive metal mesh. When your fob is inside it and the pouch is sealed, the fob broadcasts nothing — it is effectively off from the car's perspective. No signal means nothing to amplify.
A 2-pack costs around $10 and takes zero time to use — drop your keys in it each night when you get home. Test it: put the fob in, seal it, and try to open your car door from arm's reach. If the door opens, the pouch is defective or unsealed.
Most Vulnerable Car Models
Relay theft disproportionately targets high-value vehicles, but any car with passive keyless entry is technically vulnerable. Models with the highest theft rates in recent years include: Land Rover Defender, Range Rover, Land Rover Discovery, BMW 3 Series, BMW 5 Series, Mercedes C-Class, Audi A6, Toyota RAV4, Ford Mustang Mach-E, and Tesla Model 3. If your car is in this list, a Faraday pouch is essential.
Other Good Practices
Store your keys away from external walls and doors — the amplifier needs to be close. Some people store their keys in a metal tin or bowl, which provides partial but not complete shielding. A purpose-made Faraday pouch or signal-blocking box is the reliable solution. Where your car has a "PIN to Drive" or "Passive Entry Off" option in settings, enable it. A steering lock doesn't stop the theft but makes the car significantly less attractive to opportunistic thieves.