Abstract: Disclosed herein are devices, systems, and methods for the intelligent fuzzing of cyber-physical systems, including the use of artificial intelligence (AI) for such fuzzing. In at least one embodiment, a method is disclosed for intelligent fuzzing, which includes the steps of (1) characterizing “normal” behavior of the cyber-physical system being tested, which may include, for example, utilization of a causal model to analyze causal relationships between various messages sent to and/or from the system being tested, (2) identifying dependency relationships between these various messages and/or generating a dependency graph for the messages, and (3) fuzzing an incoming message from the system under test. The fuzzing process may include querying the causal model to determine if the message is contained within the model. Fuzzing may further include altering the message's contents by, for instance, randomly manipulating particular message fields and/or replacing letters with other letters.