if there's time there's a way. many cars used a shield over the linkage, honda, toyota are a couple. toyota & honda have also used a plastic tube over there linkage that slides on the linkage. pretty effective as ya can't grab the linkage to manipulate it. some newer cars use cables. that leaves the linkage as not a viable means of attact. but any car can be got into. though some are easier than others. i use a alarm so at least i know if i've been breached......but i know of no way to outright stop it from being breached......only ways to slow it down.....which in the end is all that security is about. make it too difficult to get in and maybe the criminals will go criminalize somebody else......
was also thinking about a shield over mechanism, why would they seemingly only get in on drivers side? 
