Malicious Origin of Deadlocks in Flexible Manufacturing Systems

Flexible Manufacturing Systems (FMSs) are designed to execute parallel processes simultaneously by using flexible resources (e.g. robots, re-configurable machines) alongside a supervisor allocating the resources to the different processes. In these systems, deadlocks are defined as blocking states where no resource allocation decision can be taken. They originate from resources characteristics (i.e. mutual exclusion condition, non-preemptive), processes interactions (i.e. shared resources, circular wait of resources) and an inappropriate sequence of allocation decisions. In modern FMSs, the use of open and interconnected control components for resource allocation control and productivity enhancement makes FMSs vulnerable to cyberattacks. Hence, although FMSs are designed to deal with known natural deadlocks, new malicious ones can originate from sophisticated cyber-attacks. In this paper, malicious deadlocks are defined and contextualized regarding the existing literature on deadlocks management and on cyber-attacks targeting Discrete-Event Systems (DES). Then, a model representative of deadlock attacks is proposed based on the S3PR theory and DES attacks modeling. Finally, the deadlock attack model is simulated and new malicious deadlocks are exhibited and discussed. Copyright (C) 2022 The Authors.