From the linked article: Relay thefts According to Bates, many of these thieves are using a method called "relay theft." Key fobs are constantly broadcasting

From the linked article: Relay thefts According to Bates, many of these thieves are using a method called "relay theft." Key fobs are constantly broadcasting a signal that communicates with a specific vehicle, he said, and when it comes into a close enough range, the vehicle will open and start. "The way that the thieves are getting around this is they're essentially amplifying that low power signal coming off of the push start fob," he said. "They will prey upon the general consensus that most people are leaving their key fobs close to the front door of their home and the vehicle will be in the driveway." The thief will bring a device close to the home's door, close to where most keys are sitting, to boost the fob's signal. They leave another device near the vehicle, which receives the signal and opens the car. Storing the keyfob in a faraday bag blogs the signal and prevents the relay attack from working.