A system for detecting an out-of-operation state of an elevator system, characterized in that the system comprises: a signalization sensor unit configured to obtain signalization traffic data of at least one control system bus arranged between an elevator control system of the elevator system and at least one of a car operating panel, landing call devices (220a-220n), a hoisting motion control system, a door control unit, or an elevator group control system, at least one actuation sensor device (104, 104') configured to obtain actuation output data of at least one actuator entity of the elevator system followed by the obtained signalization traffic data, an external computing entity, and a monitoring unit configured to: generate reference actuation output data followed by the obtained signalization traffic data by applying a machine learning module stored in a memory unit of the monitoring unit, wherein the machine learning module is configured to receive the obtained signalization traffic data as its input data and to generate the reference actuation output data as the output data of the machine learning module by applying one or more machine learning techniques, and generate a signal indicating an out-of-operation state of the elevator system to the external computing entity, in response to a detection of a deviation between the obtained actuation output data and the generated reference output data. a signalization sensor unit configured to obtain signalization traffic data of at least one control system bus arranged between an elevator control system of the elevator system and at least one of a car operating panel, landing call devices (220a-220n), a hoisting motion control system, a door control unit, or an elevator group control system, at least one actuation sensor device (104, 104') configured to obtain actuation output data of at least one actuator entity of the elevator system followed by the obtained signalization traffic data, an external computing entity, and a monitoring unit configured to: generate reference actuation output data followed by the obtained signalization traffic data by applying a machine learning module stored in a memory unit of the monitoring unit, wherein the machine learning module is configured to receive the obtained signalization traffic data as its input data and to generate the reference actuation output data as the output data of the machine learning module by applying one or more machine learning techniques, and generate a signal indicating an out-of-operation state of the elevator system to the external computing entity, in response to a detection of a deviation between the obtained actuation output data and the generated reference output data. generate reference actuation output data followed by the obtained signalization traffic data by applying a machine learning module stored in a memory unit of the monitoring unit, wherein the machine learning module is configured to receive the obtained signalization traffic data as its input data and to generate the reference actuation output data as the output data of the machine learning module by applying one or more machine learning techniques, and generate a signal indicating an out-of-operation state of the elevator system to the external computing entity, in response to a detection of a deviation between the obtained actuation output data and the generated reference output data.