The invention relates to a method for evaluating the authenticity of peripheral devices of a self-service machine having an operating system that provides at least one global mutex, having software layers, that are arranged on the operating system, having processes that run on the self-service machine and that access the operating system and/or the software layers, comprising the steps of: evaluating of authenticity of a connected peripheral device by a first process; if it was determined during the evaluation that the peripheral device could not be authenticated, setting of the mutex; evaluating the mutex by a second process based on an event and, if the mutex is set, switching the self-service machine to an error state.