Claim: Thieves armed with "code grabbers" can break into cars by recording signals sent by remote keyless entry devices.
In mid-2008 some anonymous person thought to add a "Snopes approved" line to the e-mail being circulated. In a nutshell, no, the item is not "Snopes approved" — we take issue with almost all of the e-mail's premise. http://www.snopes.com/autos/techno/lockcode.asp
It is theoretically possible for a very determined thief armed with the right technology and the ability to manipulate it correctly to snatch a keycode from the air and use it to enter a vehicle. However, the complexity and length of time involved in that process means your typical crook can't simply grab an RKE code in a parking lot and open up the corresponding car within a minute or two: the would-be thief would need specialized knowledge and equipment and would have to spend hours (if not days) crunching data and replicating a device to produce the correct entry code, then hope he could locate the same vehicle again once all the other steps had been completed. (In most parking lot scenarios, the target car would be long gone before the putative thief was able to open it.) As Microchip Technology, the manufacturer of KEELOQ brand RKE systems, noted of this possibility: