Where you leave your keys inside your home could make your car the target of a break-in.

The problem: As vehicles become more technologically advanced, thieves are becoming technologically savvy, too.

“Just as quickly as the cars are coming up with these technologies, we have criminals out there trying to combat it and find ways around it,” said Officer Chris Kopp of the Charlotte-Mecklenburg Police Department in North Carolina.

Cars with a hands-free key fobs typically unlock a car within about 30 centimeters, said Dave Yelverton, a spokesman for AAA Carolinas.

“Your car is continually trying to reach out and touch this key,” Yelverton said. “And when it finds the key, you can open the door without touching the car without using the key. You can just leave it in your pocket.”

But across the USA, thieves have begun using a device called a power amplifier to help unlock the cars. The amplifier, which can cost less than $20 over the Internet — takes the signal from the car and projects it as far as 100 meters, so your car can find your key fob in your purse, pocket or the table where you dump your stuff when you come in the door.

“That’s exactly right. That’s the theory behind the theft,” Yelverton said. “Someone with an amplifier could theoretically grab your key signal from your car, open the car — you’d never know it — take all your goodies, then they lock the car and leave.”

  • In Toronto, police since January found a spike in thefts from Toyota and Lexus SUVs parked in owners’ driveways with no signs of damage.
  • In Los Angeles, a reporter noticed the same problem in his own neighborhood, even watching two teens on bicycles break into his Prius as it sat on the street in front of his house.
  • In Tonawanda, N.Y., people who swore they had locked their car doors returned to their vehicles to find them rummaged through, spare change gone, but otherwise undamaged.
  • In Springfield, Mo., a rash of vehicle break-ins had residents wondering how thieves with slim jim lock picks could go through so many cars and leave no damage.
  • In Long Beach, Calif., detectives shared a video on YouTube two years ago showing break-ins of two SUVs parked in their owner’s driveway.

As more people buy cars with these no-push key fobs, what’s the solution to stopping this type of break-in? Yelverton said the type of key you have doesn’t matter but where you put it.

“Use a microwave, or you can use a refrigerator or your freezer,” Yelverton said.

The heavy metal cages around the appliances all block the amplifier, he said. It’s another case of convenience becoming a two-edged sword.

“That involves technology,” Yelverton said. “Technology can be hacked.”

Some key fobs do need to be kept at room temperature to avoid damaging their batteries, so check with your car dealer before putting yours in the fridge or freezer. Another simple alternative: Wrap your keys in aluminum foil.