Vehicle network communication protection

The invention relates to a vehicle comprising a gateway controller 120 configured to interface a diagnostic port 122 to a vehicle communication network 130. In response to a perimeter alarm system 144 being in an armed state and the ignition switch being in an off position, a microcontroller system (200, see fig 2) is programmed to inhibit transfer of messages from the diagnostic port to the vehicle communication network. The system may, in response to inhibiting transfer of messages, trigger activation of the perimeter alarm or may output a response message via the diagnostic port. The system may also be programmed to, in response to the alarm not being armed, ignition switch in the on position, and receiving a change session diagnostic request in a presence of a signal indicative of vehicle speed being less than or equal to a predetermined threshold, transmit the change session diagnostic requested on the vehicle network. The invention also relates to a method for protecting a vehicle network using the aforementioned system.