An increasing number of vehicles now use an electric power steering assist system. The most obvious purpose is as part of the “auto-parallel-park” systems, but even cars without that gadgetry have the (presumably computer-linked) electric steering hardware. It’s on-track to replace the hydraulic assist systems, at least in light-duty vehicles.
That is correct.
As I understand it, these auto park systems have a safety system that prevents injury to drivers that accidentally obstruct the steering wheel during the auto park sequence.
This should make an average driver able to overpower the power assist system by preventing the wheel from turning in the assist direction, however, but, depending on HOW the safety system works (electronic or mechanical force limitation), I cannot assert that a driver could maintain control.
I know of no hydraulic assist systems with an electronic control valve, fortunately, because no one could overpower a hydraulic system.
Anything on the CAN bus is hackable. I have seen 54 onboard computers on the CAN bus (Lexus LS 460). Imagine the power seat moving foreword and up while the tilt and telescope steering column moves back and down for example.