1. In combination with a vehicle having a data-processing system including at least one operating memory holding all of the operating data needed for controlling the vehicle, a protection unit being integrated into the data-processing system and comprising: an execution environment forming a runtime environment protected from unauthorized read and write access; at least one monitoring logic in the protected runtime environment connected to the operating memory for monitoring protection violations of the operating data stored in the operating memory and for generating an output on detection of such a protection violation; and a protection logic in the protected runtime environment holding uncompromised replacement data capable of replacing all of the operating data and holding authorization information required for use of the replacement data, only the protection logic being capable of using the replacement data to operate the data-processing system of vehicle, the protection logic being connected to the monitoring logic for, on generation of the output, executing the replacement data from the protected runtime environment instead of the operating data in the operating memory for controlling the vehicle or replacing the operating data in the operating memory with the replacement data and executing the replacement data from the operating memory for emergency operation independent of the replaced operating data.