# Security Challenges in Industry 4.0 PLC Systems
## 1 Introduction  
The beginning of the first industrial revolution is dated as from the end of the 18 th century and was driven by mechanical production plants based on steam power. At the beginning of the 20 th century, there was a second revolution based on mass labor production using electrical energy. Then the third industrial revolution began in the 1970s and was driven by automatic production based on electronics and internet technology. Nowadays, the fourth industrial revolution, namely Industry 4.0, is happening. The idea of Industry 4.0 was initially proposed as a means of developing the German economy in 2011 [1; 2; 3; 4; 5; 6; 7]. The fourth industrial revolution places increasing expectations on governments resulting from the new role of the state in the economy and its involvement in solving problems of unreliable markets [8], with the key issue being the management and effectiveness of the state's activities, rather than the state size. Industrial policy being implemented by many countries is de facto aimed at reorienting national economies towards a fourth generation of industry [9], be it with a view to preserving and restoring jobs or by trying to improve competitiveness and added value of domestic production. The possible benefits are not only an improvement in efficiency, a reduction in errors, lower demand for raw materials and cost reduction, but also an opportunity to sell your own solutions to cooperators and clients. Transformation towards Industry 4.0 in the long run will bring measurable effects in the form of a higher rate of return on the invested company capital [9]. The road to reach such goal is, however, very difficult, following from the nature of the Industry 4.0 concept. Such transformation imposes not only technological challenges but also organizational [10; 11] and sociological [12; 13; 14] ones. While aiming to achieve a higher level of automatization and operational productivity [15], the Industry 4.0 concept requires vast computerization, inter-connection and horizontal and vertical integration in the traditional industry [4]. Production in Industry 4.0 can be treated as a cyber-physical system (CPS) [16; 17] based on heterogeneous data and knowledge integration [4; 6]. CPS is defined as a set of transformative technologies for managing interconnected systems between its physical assets and computational capabilities [18]. It creates an interoperable, optimized adaptive and scalable manufacturing process that is usually service-oriented [19]. It allows for an intelligent flow of produced elements between machines in a factory with real-time communication between machines [20]. Such systems require and are based on new technologies (see Figure 1), such as the Internet of Things (IoT) [21; 22; 23; 24; 25; 26; 27; 28] and Services (IIoS) [29; 30], Big Data (BD) [31; 32; 33], Edge/Fog/Cloud Computing [34; 35; 36; 37; 38; 39; 40; 41; 42; 43], Blockchain [44; 45; 46; 47; 48], Industrial Automation, Cybersecurity [49; 50], Intelligent Robots and Cobots [51; 52; 53]. All the technologies mentioned above are essential for achieving the desired benefits of adopting Industry 4.0 in factories and in the whole value production chain. Application of such technologies requires, however, tight integration using networking solutions. This is why Industry 4.0 will face traditional cybersecurity issues and some other new ones following the nature and scope of the systems integration. If these solutions are not addressed properly, the true potential of the new industrial revolution may never be achieved. The most significant challenge related to cybersecurity is the integration and cooperation amongst the stakeholders of any given Industry 4.0 organization. All participating environments are made of diverse technologies spread across many disciplines with many different types of subject-matter experts; however, there are few standards and processes designed to assist each entity to communicate with respect to the high standards of cybersecurity [55].