Resilience against cyberattacks is an important requirement of modern cyber-physical systems (CPS) considering the industry 4.0 evolution. In this work, we use the formalism of Discrete Event Systems (DES) to design an approach that aims to protect cyber-physical systems against actuator attacks using event-based symmetric cryptography. In this approach, controllable events that are properly selected are encrypted before being transmitted from the controller to the plant, leading intruders to mistakenly infer the supervisor’s control actions. Thus, it is presumed that attacks on actuators do not have the expected impact on the plant, preventing unsafe states from being reached. The proposed approach is applied to a case study from the literature, where the identification of the attack is done without causing any damage while maintaining the integrity of the system.