I. Introduction
In the past decade, there has been a significant increase in security and safety incidents in industrial environments and critical infrastructure. Some of these incidents have led to devastating consequences, such as the Stuxnet (2010) [1] computer worm’s takeover of several Programmable Logic Controller (PLCs), resulting in the destruction of centrifuge tubes at a uranium enrichment plant in Iran. Malware attacks like BlackEnergy (2015) [2] and Industroyer (2016) [3] on Ukrainian power grids caused outages that affected thousands of users. These events highlight the vulnerability of critical infrastructures to cyber-attacks, as well as the need for effective means of detecting spurious behaviour that may represent the first signs of a threat.