system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: With the advancement of driverless cars and other autonomous aspects growing daily, what exactly stops somebody from hacking into the network and controlling it?

I've seen plenty of apocalyptic or otherwise sci-fi movies/games where it all started with a a society core networks being hijacked and otherwise. I also read about the advancement of quantum computers which would really render all current forms of cyber security obsolete due to the amazing processing power they would have to break the security. So really what I'm getting at is if in 10 years we all have driverless cars, all from differing car companies with differing software and some evil genius creates a powerful quantum computer on his own, what's stopping him from taking control of all the cars or similarly disastrous technologies?
Obviously I only read articles on the matter and really as I type this just sound incredibly paranoid but still.
gpt
billion dollars industries spend a lot on security. the answer is the same as if you'd have asked "now that all money is digital, how come someone just doesn't hack millions of dollars into their account"