Car Doctor Q&A: Can a Faraday Cage Prevent Car Break-Ins?

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Remote door locks are pretty much a standard feature these days, but their convenience leaves your car vulnerable to break-ins. Car Doctor John Paul has some security suggestions.

Q. There was a rash of auto break-ins in our residential neighborhood this week. All of the vehicles broken into were apparently the result of sophisticated thievery.

It appeared that the break-ins were done electronically as there was no evidence of physical methods. The police confirmed that some other recent auto break-ins have been done electronically. Luckily, the thieves were only interested in cash and didn’t do any damage to the vehicles. From what we’ve heard, nothing was taken except for a roll of parking meter quarters. They even passed up a GPS unit and phone chargers.

The cars were of various late model brands (Chevy, Kia, Honda, Saab) but all have keyless entry. Obviously, this tell me, there are methods to defeat current keyless entry systems, this despite contrary claims by the car manufacturers. Can you suggest some ways to deter these thieves.

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A. Thieves have used code grabbers for years to intercept the key fob code, but the thief needs to be near the vehicle to intercept and then “rebroadcast” the code to get into the car.

Many vehicle manufactures have moved to rolling code system which can prevent this, by changing the code each time the fob is used. But just like anything there is a hack for this that jams the code and prevent it from rolling, but again the thief needs to be nearby.

The other issue is with proximity key fobs, the type you keep in your pocket that recognize you are you walk up to your vehicle. With this system there is an antenna/transmitter in the car that looks for the key fob. Typically the vehicle can detect the key fob from a couple of feet away.

What some high-tech thieves are using is an amplifier (carried in a backpack) that can detect the key fob at a much great distance, fooling the car into thinking the key is close by. I have personally seen this amplifier made for less then $100 in salvaged electronic parts.

The best protection against this type of thievery is to keep you key fob in a Faraday cage/shield. This cage blocks the radio transmission signals.

The name “Faraday cage” implies that you need to have some kind of gigantic mesh device in your home. These days, you can buy a Faraday bag specifically for storing your car keys for $15 to $20.

Regarding deterring theft, my friends in law enforcement tell me that most cars are unlocked and many have the keys in them. My suggestion is to always lock your car, remove any valuables from sight and park in well lighted areas.

Then again you could buy a really ugly car or get a big mean dog.

John Paul is senior manager of public affairs for AAA Northeast. A certified mechanic, Paul tests dozens of new cars each year and also hosts a radio show on AM 950