keep your tin foil hat on,
Can it be done, Yes, on SOME cars, I have two that use an IR sensor no RF, try to intercept that!!!
And then even if they did intercept my cars that use RF, all they could do is open the car. Starting the car needs an RFID chip that does NOT transmit, and must be near the ignition to allow the car to start, along with in most cases needing a key.
I've got thousands of things I'm going to worry about before someone intercepting my car signal!!!
Meanwhile I'll leave my tin foil hat in a faraday shield in the attic! something for the kids to wonder about.
and geting a key for my vehicles requires going to a dealer with proof of ownership, getting picture taken, signature taken and kept on file and then waiting at least 24hours for a key to arrive.
Even virtually all locksmiths around here IF they can duplicate the chip key require proof of ownership, picture etc. if they are going from VIN number instead of a key to duplicate.
And in the highly highly unlikely case someone did manage to get my vehicles, I can track the location of any of them and police can then follow and if needed continually reduce the speed allowed by the vehicle till it is down to less than 5 mph.
I'm not worried.