Development of an Original Theoretical Model for Cascaded Fault Propagation in Networked Industrial Cyber-Physical Systems Under Adversarial Cyber-Physical Attacks

Industrial cyber-physical systems such as those controlling oil refinery operations and electricity distribution networks in Nigeria represent complex networked infrastructures where cyber-domain attacks can propagate into physical domain consequences through cascaded failure mechanisms that are inadequately modelled by existing fault propagation theory developed for purely physical or purely cyber system contexts. This dissertation develops an original theoretical model for cascaded fault propagation in networked industrial cyber-physical systems under adversarial cyber-physical attacks, grounded in interdependent network theory, stochastic hybrid system formalism, and attack-graph-based threat modelling. The model represents a CPS as a bipartite network of cyber and physical components with interdependency edges that define causal propagation channels between domains. A stochastic hybrid system framework captures the discontinuous state transitions induced by attack events and the continuous physical dynamics that evolve between events. Novel theoretical results are derived characterizing the critical interdependency density threshold above which cascaded failures exhibit self-amplifying propagation behaviour that cannot be arrested by localized isolation countermeasures. The model is parameterized and validated using incident data from three documented cyber-physical attacks on Nigerian critical infrastructure systems, including the 2023 substations communication network intrusion event. Optimal defence resource allocation policies derived from the theoretical model are compared against industry-standard defence-in-depth heuristics on a simulation testbed representing the Escravos gas processing facility network topology. The dissertation contributes the first analytical characterization of CPS cascaded failure criticality thresholds informed by Nigerian critical infrastructure empirical data. Keywords: cyber-physical systems, cascaded failure, adversarial attack, fault propagation, critical infrastructure