Cyber attack modelling and security graded approach: key elements when designing security architecture for Electric Power Utilities (EPUs)

摘要

The multiplication of access interfaces and technologies in Electric Power Utilities (EPUs)communication architectures and the smart grid developments, which will enable numerous newservices with new traffic patterns, will change radically both network accesses and core architectures.This evolution could introduce new vulnerabilities to the reliability of electricity supply, based on theintroduction and exposure of vulnerabilities in digital systems, architectures, and communications.This situation calls for new security requirements for digital systems and the underlying architectureused in EPUs. Security requirements have to be derived from appropriate risk assessments and generalarchitectural decisions. Numerous existing cyber security standards provide guidance and use-caseswhich represent valuable inputs for the development of such requirements. The proliferation ofstandards suggests, however, that the existing documents either do not meet completely the needs ofEPUs or are difficult to combine together. This paper focuses on two weak points of the existing cybersecurity standards in the area.Initially, the paper addresses the characterization, categorization and modeling of malicious cyberthreats, which represent key steps in a risk assessment process. The paper presents a conceptual modelexpressing the meaning and the links between the key concepts of cyber security risks. Following this,the work examines attack modeling, addressing some pertinent technical and architectural issues. Inaddition, the paper explains why attack modeling is central to risk assessment and present graphicalapproaches to attack modeling.The second part the paper addresses the use of security architecture principles, notably the gradedsecurity approach as a fundamental framework to classify and structure a process of risk mitigation bysecurity controls in both current and future EPU architectures. This discussion starts with theclarification of the terminology related to a graded security approach and then gives a generaloverview of the characteristics of known standards and best practices of graded security architectures.Following this, the paper presents an outlook of classification criteria to enable the implementation ofa graded security approach in a real world environment and then illustrates the effectiveness andadaptability of a graded security approach in a real-world attack case.