It's going to get worse - on most cars the CAN bus is not encrypted and the messages are not signed. There was a comment here recently where a tech in the auto industry claimed that one manufacturer was planning to start signing the CAN bus packets. That will mean it likely becomes impossible to do things like re-code the PCM for a motor with a different VIN so you can re-use the PCM in another vehicle.

That will be quite hard to overcome.