Modeling and Vulnerability Analysis of Spatially Embedded Heterogeneous Cyber-Physical Systems With Functional Dependency

Modern infrastructures are always spatially embedded and coupled with auxiliary information systems to form heterogeneous cyber-physical systems (CPSs). In this paper, considering the spatial information and overlap of components, a heterogeneous cyber-physical system model with weak dependency is proposed, in which the two networks overlap geographically and have heterogeneous models. Based on the connectivity between their dependent cyber nodes and the control center, the physical edges are classified as controllable or uncontrollable, corresponding to global and local load transfer strategies, respectively. Combined with coordinated DoS (deny of service) attacks on cyber nodes, the system vulnerability under physical edge-removal and edge-overload scenarios is investigated. It can be concluded that although the two networks are weakly dependent without direct failure-induced dependency, a fragmented cyber system can still aggravate the failure of the physical system. In the edge-removal scenario, deliberately attacking high-load edges produces better results, while imposing extra load on low-load edges performs better in the edge-overload scenario. In addition, blocking specific cyber nodes that make attacked edges or their adjacent edges uncontrollable can effectively improve the attack effect. This model might yield insight into modeling and protecting spatial cyber-physical systems.

I. Introduction

NETWORKS are ubiquitous in the real world [1], [2]. In many infrastructures, nodes are interconnected to form complex networks [3]–[6] that realize the transfer and transmission of flow to maintain functions, such as traffic flow, power flow and information flow. In recent decades, with the development of communication, computer and control (3 C) technologies, a large number of physical devices are equipped with intelligent electronic devices (IEDs) [7], [8]. In the Internet of Things (IoT) [9], in addition to physical systems (networks), additional communication and control systems (networks) are also required to form cyber-physical systems (CPSs) [10]. Among them, the physical network is the main body of the system, which is responsible for the realization of physical functions, such as power supply and communication. As an auxiliary system of the physical network, the cyber (information) network is responsible for status monitoring and data transmission of the physical system as well as optimization and command issuing from the control center. For example, in cyber-physical power systems (CPPSs) [11], [12], the power grid realizes the generation and transmission of electricity, and the cyber network enables the monitoring of power nodes and the optimization of power flow. Similarly, in cyber-physical transportation systems, the cyber network facilitates the control and optimization of traffic flow, such as the control of traffic lights and the evacuation of congested roads.