Pirates of the MQTT: Raiding IIoT Systems with a Rogue Client

The integration of MQTT (Message Queuing Telemetry Transport) in Industrial Internet of Things (IIoT) systems enhances operational efficiency but introduces significant security vulnerabilities, particularly through rogue MQTT clients. These clients exploit MQTT weaknesses to disrupt industrial processes and compromise data integrity. This paper examines the impact of rogue MQTT client attacks, demonstrated through a detailed case study using the Fischertechnik Lernfabrik 4.0. We highlight how attackers can exploit MQTT's inherent vulnerabilities, including anonymous connections and message retention, to inject false data and interfere with operations. To address these risks, we propose several mitigation strategies: implementing fine-grained authorization for topic access control, enhancing replay attack protection with Message Authentication Code (MAC), employing mutual TLS (mTLS) for secure client authentication, and incorporating real-time client activity monitoring and anomaly detection. These measures aim to bolster IIoT system security, mitigate potential disruptions, and maintain operational integrity. Our findings and recommendations contribute to advancing security practices in MQTT-based IIoT environments. All attack codes and a proof-of-concept are ublicly available.