Re: Crash to stop insurance price hike
Most CAN transceivers have a passive mode for read-only but it's a software controlled feature. So your hackers could change it to get write access. I don't see what you could do in hardware to prevent this.
It strikes me there should be a manufacturer-provided port for this function based off an additional can-bus with copies of the relevant data. Anything writing to that would have no effect on the vehicle.