Security measurement of instrumentation systems: A case study of NPP

Current instrumentation systems are distributed in nature and hence consist of different processing nodes that are interconnected with each other to exchange the data. The input data is processed into a meaningful data and output to other processing nodes. The output of the nodes depends on the input data and hence the validity of the input data needs to be ensured for the correct functioning of the overall system. Many of the instrumentation systems are safety critical in nature and contains confidential data and hence it must be secure from outside access. Due to the security significance of these systems, there is a need to assure the secrecy of systems at an early stage. In order to improve the security of instrumentation systems, this paper introduces a threat-driven modelling framework to measure the security threats using Petri Net. The technique has been validated on 21 instrumentation systems of Nuclear Power Plant and illustrated on a case study in this paper.