**Abstract**

Information and communication technology (ICT) plays an important role in critical infrastructures (CIs). Some ICT-based services are in itself critical for the functioning of society while other ICT elements are essential for the functioning of critical processes within CIs. Moreover, many critical processes within CIs are monitored and controlled by industrial control systems (ICS) also referred to as operational technology (OT). In line with the CI-concept, the concept of critical information infrastructure (CII) is introduced comprising both ICT and OT. It is shown that CIIs extend beyond the classical set of CIs. The risk to society due to inadvertent and deliberate CI/CII disruptions has increased due to the interrelation, complexity, and dependencies of CIs and CIIs. The cyber risk due to threats to and vulnerabilities of ICT and OT is outlined. Methods to analyze the cyber risk to CI and CII are discussed at both the organization, national, and the service chain levels. Cyber threats, threat actors, and the organizational, personnel, and technological cyber security challenges are outlined. An outlook is given to near future cyber security risk challenges, and therefore upcoming risk, stemming from (industrial) internet of things and other new cyber-embedded technologies.

**Keywords:** critical information infrastructure, cyber, risk, critical infrastructure, operational technology, industrial control systems, SCADA, internet of things, industrial internet of things, security, mitigation
