ICSML: Industrial Control Systems Machine Learning inference framework natively executing on IEC 61131-3 languages

Industrial Control Systems (ICS) have played a catalytic role in enabling the 4th Industrial Revolution. ICS devices like Programmable Logic Controllers (PLCs), automate, monitor and control critical processes in industrial, energy and commercial environments. The convergence of traditional Operational Technology (OT) with Information Technology (IT) has opened a new and unique threat landscape. This has inspired defense research that focuses heavily on Machine Learning (ML) based anomaly detection methods that run on external IT hardware which means an increase in costs and the further expansion of the threat landscape. To remove this requirement, we introduce the ICS Machine Learning inference framework (ICSML) which enables the execution of ML models natively on the PLC. ICSML is implemented in IEC 61131-3 code and works around the limitations imposed by the domain-specific languages, providing a complete set of components for the creation of fully fledged ML models in a way similar to established ML frameworks. We then demonstrate a complete end-to-end methodology for creating ICS ML models using an external framework for training and ICSML for the PLC implementation. To evaluate our contributions we run a series of benchmarks studying memory and performance and compare our solution to the TFLite inference framework. Finally, to demonstrate the abilities of ICSML and to verify its non-intrusive nature, we develop and evaluate a case study of a real defense for process aware attacks against a Multi Stage Flash (MSF) desalination plant.