Edinburgh Napier University

  Critical infrastructures such as nuclear plants or water supply systems are mainly managed through electronic control systems. Such systems comprise of a number of elements, such as programmable logic controllers (PLC), networking devices, and actuators. With the development of online and networking solutions, such electronic control systems can even be managed online. Even though network connected control systems permit users to keep up to date with system operation, it also opens the door to attackers taking advantages of such availability. In this paper, a novel attack vector for modifying PLC memory is proposed, which affects the perceived values of sensors, such as a water flow meter, or the configuration of actuators, such as a pump. In addition, this attack vector can also manipulate control variables located in the PLC working memory, reprogramming decision making rules. To show the impact of the attacks in a real scenario, a model of a clean water supply system is implemented in the Festo rig. The results show that the attacks on the PLC memory can have a significant detrimental effect on control system operations. Further, a mechanism of detecting such attacks on the PLC memory is proposed based on monitoring energy consumption and electrical signals using current-measurement sensors. The results show the successful implementation of the novel PLC attacks as well as the feasibility of detecting such attacks.