LAUSR

Abstract Programmable logic controllers (PLCs) are important components of industrial control systems (ICSs), which are digital electronic devices with microprocessors and lack network security considerations. With the explosion of cyber-attacks on the ICS network, the concept of the worm known as PLC-PC worm that can spread between the Internet and ICS network has attracted a great deal of attention. In this paper, for the first time, we propose a propagation model to explore the spread behavior of PLC-PC worms across the PLC-PC coupled network. Theoretical analysis of the model shows the disease-free and endemic equilibriums of the network with defensive measures. And the stability of the model is examined by an epidemic threshold value. Several numerical and simulation experiments are presented to illustrate the analysis. Based on the results, some ideas for restraining the spread of PLC-PC worms or reducing the security threats of the ICS network are suggested.