Method and apparatus for monitoring a bus system and a bus system

The monitoring method has at least one subscriber (101,103) of the bus system (100), e.g. a controller area network bus system, designated as an authorized subscriber and used for monitoring the data transmission along the bus system, each of which is provided with a subscriber identification, compared with given identifications, for blocking data transmission by an unauthorized subscriber. Also included are Independent claims for the following: (a) a bus system monitoring device; (b) a bus system provided with a monitoring function