I highly doubt alCIAda or any
I highly doubt alCIAda or any other terror group is going to go after cars on a mass scale. There are far better ways to carry out acts of terrorism. You can't take over a car and steer it to propel it into anything. You can, at best, activate its (anti-lock) braking system, stopping it on a highway, or slow it down/turn off its engine. Yes, if you were fast enough (good luck), you could hack three or four cars and potentially shut down a freeway. Not likely.
Given the security problems at most of our nation's infrastructure points (water, gas, sewer, etc) I'd find it far more likely that someone hoping to carry out a mass terror attack would target something more useful than your family sedan for the purpose.
Besides, given the statistics, you're far more likely to have something fall on your car and kill you than you are to be the victim of a terror attack in the U.S. Assuming you don't consider the IRS a terror organization, haha.