By Jim Donovan

By Jim Donovan

PHILADELPHIA (CBS) — Improvements in technology have helped reduce the number of stolen cars over the last 20 years, but technology is also making it easier for thieves to steal your car as well, and in a way you can’t stop.

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Authorities are seeing an increasing number of break-ins like this one: two men get into two cars with ease – holding nothing but a small box in their hands.

Two years ago Michael Shin captured footage of a man opening his car holding a back pack. No break in tools needed.

Shin says he always locked it.

“It’s just a little unnerving that they could so easily just walk into my car and pretty much without any recourse, without anybody really noticing,” Shin said.

It wasn’t clear how this was happening, but now insurance investigators believe criminals are taking advantage of modern key fobs that allow owners to unlock their car and start it with the push of a button.

“You can’t stop this kind of theft right now,” said Roger Morris with the National Insurance Crime Bureau.

He says two devices can be used to mimic a key fob.

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A recreation shows a man getting out of his car and using the fob to lock it. Morris, in the blue jacket, uses a relay box to intercept the fob’s code.

The code is then immediately sent to a second man with a small box that now acts as the vehicle’s fob, allowing him to unlock the car, open the door, start the car and drive away.

“We tested 35 vehicles, 18 of them we were able to start with the device as well and drive off,” said Morris.

These boxes came from a company that works with law enforcement, but Morris believes professional criminals have figured out how to make their own.

They can be used to take a vehicle immediately, or crooks can save the code and steal the car later on.

“Today’s cars are basically computers on wheels, and if they can hack into that system and defeat it, they will try to continue to do that all the time” said Morris.

These devices may explain a recent increase in car thefts and law enforcement have yet to figure out how to stop it.

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The National Insurance Crime Lab says drivers who own vehicles with this technology should be careful when they lock their vehicles, and look for anyone near them acting suspiciously or carrying a strange device.