A method, system, and computer program product for behavior-based Internet of Things (IoT) device security are provided. The method detects an action from a set of IoT devices. A context is identified for the action and at least one IoT device of the set of IoT devices. The action and the context are validated for the at least one IoT device. The action is identified as an anomaly based on the validating of the action and the context. A potential state change is identified for the at least one IoT device based on the anomaly. The method determines a responsive action based on the potential state change and the anomaly.