In the digital era, Critical Infrastructures (CIs) are operating under the premise of robust and reliable ICT components, complex ICT infrastructures and emerging technologies and are transforming into Critical Information Infrastructures (CIIs) that can offer a high degree of flexibility, scalability, and efficiency in the communication and coordination of advanced services and processes. The increased usage of information technology in modern CIIs means that they are becoming more vulnerable to the activities of hackers and other perpetrators of cyber-related crime (cyber criminals). Several recent studies have shown that the landscape of cyber threats is changing continuously and the nature of attacks of this sort are evolving, involving a great degree of persistence and (technical) sophistication.
In addition to this, barriers to entry for would-be cyber criminals are falling rapidly, and nowadays, the attackers have a range of (technical) capabilities and substantial resources at their disposal, since malware and malware-as-a service become more easily and cheaply available through various means and sources (such as Dark Web, Deep Web). Thus, a variety of advanced techniques and tools (e.g. social engineering techniques and zero-day exploits programs) are available and can be used by the cyber criminals to initiate advanced targeted attacks. These threats employ multiple technologies and malware, deployed in multiple stages, to bypass traditional security mechanisms in order to penetrate an organization’s defenses. The attack vectors vary significantly including Application-Layer, Social Engineering Unauthorized Access, Malicious Code, and Reconnaissance and Networking-based service attacks that target applications, host and client operating systems, and even networking equipment. In this vein, the attackers use these techniques to get valuable data assets, such as financial transaction information, user credentials, insider information etc.