An efficient MQTT framework for control and protection of networked cyber-physical systems

As more components of Cyber-Physical Systems (CPSes) get interconnected, their protection becomes imperative. For instance, Networked CPSes (NCPSes) which consist of multiple CPSes have greater attack surfaces given the added communication layer among member CPSes, and the inter-dependency between their physical and cyber subsystems. In particular, an attack on one subsystem may affect both. While there are many studies for CPS attack mitigations, NCPS attack scenarios were under-explored due to limitations of testbed development capabilities. To address this need, in this paper, an NCPS environment comprising two remote, identical IEEE 9-bus CPS testbeds is created. It is connected over a unique framework that uses Message Queueing Telemetry Transport (MQTT) protocol for secure communication. One CPS, called the 'controlling' testbed, provides relay settings for the other CPS which is called the 'controlled' testbed. To analyze the attack behaviors, at the communication level, message integrity, delay and packet drop attacks are conducted on this controlled testbed. These attacks trip the testbed's relays, triggering four coordinated, sequential scenarios at both cyber and physical subsystems that ultimately result in cascading failures. The paper's primary contribution lies in demonstrating the feasibility of coordinated cyber-physical attacks on a NCPS, and evaluating the proposed communication framework under such scenarios. The experiment results indicate that NCPS brings advantages in detecting and mitigating known attacks to CPSes.