I have a Volkswagen T3 from '84 and the most complicated "computerized" part is bus of relays.
Yet the car is trivial to break into. Hell, I've locked myself out a few times and the Key from another T3, a key from a bycicle lock and a nail-file could open the car (but not start it).
My countermeasures are mechanical too, though: hidden circuit breaker, a lock on the steering wheel, one on the gas-pedal and one on the hand-break. All of them easy to circumvent, given some time, but that's one thing thieves often don't have: time to figure out unknows and weird stuff. Actual "security by obscurity" in a way.
Yet the car is trivial to break into. Hell, I've locked myself out a few times and the Key from another T3, a key from a bycicle lock and a nail-file could open the car (but not start it).
My countermeasures are mechanical too, though: hidden circuit breaker, a lock on the steering wheel, one on the gas-pedal and one on the hand-break. All of them easy to circumvent, given some time, but that's one thing thieves often don't have: time to figure out unknows and weird stuff. Actual "security by obscurity" in a way.