IEC 62645:2019 establishes requirements and provides guidance for the development and management of effective security programmes for I&C computer-based systems for NPPs, possibly integrating HPD (HDL (Hardware Description Language) Programmed Devices), hereinafter named I&C CB&HPD systems. Inherent to these requirements and guidance is the criterion that the power plant I&C CB&HPD system security programme complies with the applicable country's I&C CB&HPD security requirements. The primary objective of this standard is to define adequate programmatic measures for the prevention of, detection of and reaction to malicious acts by digital means (cyber attacks) on I&C CB&HPD systems. This includes any unsafe situation, and equipment damage or plant performance degradation.