## 2 Critical Infrastructures
### Critical Infrastructures and Industry 4.0  
Throughout history, societies have continuously evolved, and this natural progression has significantly impacted the industrial sector. The industrial sector itself has undergone four distinct and challenging periods of transformation. The initial period, from 1784 to the mid-19 th century, witnessed the introduction of steam-powered machinery, revolutionizing mechanical manufacturing. The second phase, spanning from the late 19 th century to the 1970s, marked the era of electric-powered mass production, characterized by assembly lines and division of labor. The third period, from the 1970s to the present day, witnessed remarkable advancements in electronics, information technology, and automation of complex tasks. As societies progress, the industrial sector remains at the forefront of innovation, shaping the course of human development and ushering in new opportunities and challenges. Today, humanity stands at the threshold of a new era known as the fourth industrial revolution or Industry 4.0 [14; 15].  
Industry 4.0 (I4.0) was initially introduced in 2011 as a strategic initiative by the German government. Since then, various other nations have followed suit with their initiatives, including the United States' Advanced Manufacturing Partnership, China's Made in China, Britain's Smart Factory, and Japan's Super Smart Society. Today, the concept of the fourth industrial revolution is being embraced by all developed countries. The essence of Industry 4.0 lies in its aim to transition from centralized production to a more flexible and self-controlled approach. This evolution is a logical outcome of the progress made in computer-integrated manufacturing and flexible manufacturing systemsover the past decades and the widespread adoption of digitization in recent years. It is worth noting that the development of I4.0 solutions and technologies has not only benefited the manufacturing sector but has also had a positive impact on the service sector, where applications like big data solutions in banking and marketing have emerged [16].  
As expected, critical infrastructures are interconnected with this important industrial evolution. The concept of Industry 4.0 plays a vital role in critical infrastructure, as some of its technologies are already or will become integral parts of various sectors. These technologies include industrial automation, robotics, sensors, cyber-physical systems, Industrial Internet of Things (IIoT) [17], big data, block chain, edge computing, digital twin, and artificial intelligence, which are widely considered in manufacturing and service industries [18; 19; 20; 21]. However, the adoption of Industry 4.0 solutions in critical infrastructure also introduces potential risks that need to be carefully addressed, such as cybersecurity and reliability concerns [14; 22]. A pivotal aspect of Industry 4.0 is the IIoT. The Industrial Internet of Things plays a crucial role in the advancement of critical infrastructures through the utilization of intelligent sensors, fast communication protocols, and robust cybersecurity mechanisms. The establishment and effective management of sensor networks form the foundation of IIoT, making it a significant component that profoundly influences both Industry 4.0 and critical infrastructures.