Here are a few keys and remotes that we’ve programmed recently
Modern vehicles have immobilisers fitted to prevent theft. These immobilisers look for a transponder chip in the key or the remote. It must be the exact same chip programmed into the vehicle for it to start. Although somebody else’s key may open your locks (a slim possibility) it will not start your vehicle unless your immobiliser has been previously been programmed to accept it. The metal part of the key is very cheap to replicate. To replace the transponder can involve quite a lot of work.
The latest type vehicles with smart remotes that you can keep in your pocket are actually quite vulnerable to theft. It is possible that a thief can steal your vehicle if your remote is in range. These smart / proximity remotes should not be kept within range of your vehicle. Keep them at the back of the house, or invest in a blocker bag, or metal box.