Seaver

There are separate devices that only listen. Think of cell phone listeners, they can be set to listen to various frequencies. Now just think of a computer chip inside which just listens and can determine which are not simply static, then saves those for playback. If they have the right frequency they just alternate the signal.

The signal is extremely basic, usually no more than a few bits of information. So they just sit there on that frequency and wait for the unlock blinkers to pop.

People use the EXACT same method for garage door openers. They will sit on a street and listen when people leave, then just hit it again in a little while. Even easier is to buy extra remotes for every major garage door opener compnay (since each only have 2 different signals to keep cost down). They buy each and just click until a door opens.

However garage door companies have gotten smart recently and now offer devices which alternate both frequency and sequence code every time it's used. While not impervious, it's a relatively easy way to greatly increase your security. Someone can steal loads of stuff from inside your garage without drawing attention. If they carry through the front door to a waiting van people would get suspicious.

I'm not quite sure what you mean. To protect yourself just roll up the windows and lock the door as you're getting out of the car. By using the buttons inside the car nothing is spread through radio waves, so they have no way to access it (without being extremely lucky).

The methods I was talking about is when people simply walk away from their car and use the remote locks as they're walking away. If you're walking to your car, the unlock for the remote is safe considering you're heading to the car someone could be wanting to get into. They dont want confrontations if they're using this method, so they'll sit and wait for the next person who uses the remote locks.