Didn't that Wired article about the Jeep hack tell us something about how well that sometimes gets implemented?
From memory, there was an "untrusted trusted entertainment system" network segment, and a firewall which allowed one-way traffic out of the "trusted" vehicle management network (so the entertainment system could get car speed and similar), and the firewall could have it's firmware updated. From the untrusted network segment...
From memory, there was an "untrusted trusted entertainment system" network segment, and a firewall which allowed one-way traffic out of the "trusted" vehicle management network (so the entertainment system could get car speed and similar), and the firewall could have it's firmware updated. From the untrusted network segment...