. . "As new technologies such as the Internet of Things (IoT) are integrated into Critical National Infrastructures (CNI), new cybersecurity threats emerge that require specific security solutions. Approaches used for analysis include the modelling and simulation of critical infrastructure systems using attributes, functionalities, operations, and behaviours to support various security analysis viewpoints, recognising and appropriately managing associated security risks. With several critical infrastructure protection approaches available, the question of how to effectively model the complex behaviour of interconnected CNI elements and to configure their protection as a system-of-systems remains a challenge. Using a systematic review approach, existing critical infrastructure protection approaches (tools and techniques) are examined to determine their suitability given trends like IoT, and effective security modelling and analysis issues. It is found that empirical-based, agent-based, system dynamics-based, and network-based modelling are more commonly applied than economic-based and equation-based techniques, and empirical-based modelling is the most widely used. The energy and transportation critical infrastructure sectors reflect the most responsive sectors, and no one Critical Infrastructure Protection (CIP) approach \u2013 tool, technique, methodology or framework \u2013 provides a \u2018fit-for-all\u2019 capacity for all-round attribute modelling and simulation of security risks. Typically, deciding factors for CIP choices to adopt are often dominated by trade-offs between \u2018complexity of use\u2019 and \u2018popularity of approach\u2019, as well as between \u2018specificity\u2019 and \u2018generality\u2019 of application in sectors. Improved security modelling is feasible via; appropriate tweaking of CIP approaches to include a wider scope of security risk management, functional responsiveness to interdependency, resilience and policy formulation requirements, and collaborative information sharing between public and private sectors."^^ . "A Review of Critical Infrastructure Protection Approaches: Improving Security through Responsiveness to the Dynamic Modelling Landscape"^^ . . . . . . . "2019-07-02" . . . . . . . . . . . . . . . . . . . . . . .