An Overview of Methodologies for Cybersecurity Vulnerability Assessments Conducted in Nuclear Power Plants

摘要

After reviewing regulatory guidance from the NRC, VA practices in non-nuclear digital control systems, and the commentaries of other experts in the field, we conclude that established VA methodologies are inadequate as is for usage in the digital I&C systems of modernized NPPs. Current regulation establishes safety systems that are substantially hardened against outside attacks, by utilizing one-way communication and locked and alarmed physical access. However, these systems remain vulnerable to potential self-generated incidents, such as those occurring at the Browns Ferry NPP. Additionally, non-safety and data acquisition systems require further hardening as they are more exposed by defense-in-depth strategies, yet are still vital for operations. We propose that the methodologies established by the NRC can be most improved by more fully investigating the interconnectivity of all digital system components, reevaluating and redefining the risk associated with these components, and continually monitoring the security of the system throughout the entire lifetime of the NPP.