Method and device for operating a communications network

A device and method for operating a communications network in a vehicle, or for operating an industrial communications network; a control entity for the communications network, in particular, a software-defined networking controller, determining a countermeasure after detection of an attack; an infrastructure component being configured as a function of the countermeasure, in particular, by setting at least one filtering, blocking or forwarding rule; and at least one data stream from or to at least one other infrastructure component being isolated by the infrastructure component, in a portion of the communications network; or at least one data stream to or from an end node being isolated by the infrastructure component, in a portion of the communications network.