## 2 Literature Review
### Industry 4.0 and Cybersecurity Challenges  
Industry 4.0 refers to the trend of smart manufacturing through connecting cyber-physical systems, the Internet of Things, cloud computing, and cognitive computing. This enables efficiency across the production cycle via digital connectivity and data exchange. Smart sensors integrated into machinery allow for self-monitoring and optimization. End-to-end digital integration spans the full product lifecycle. Key technologies include cyber-physical production systems (CPPS) like smart machines communicating over networks, IoT sensors for data collection, cloud platforms for flexible analytics of large datasets, and advanced techniques like predictive models, diagnostics, and decision-making. The ideal aim is for higher productivity through integrated smart factories leveraging real-time digital technologies and connectivity across research, design, production, logistics, and service. Industry 4.0 integrates operational technology on factory floors with IT systems for capabilities like predictive maintenance, intelligent supply chains, and autonomous optimization [22]. As industrial organizations adopt Industry 4.0 initiatives and integrate their operational technology (OT) environments with Information Technology (IT) systems, the level of connectivity and data exchange increases substantially. More OT devices like sensors, controllers, and machines are networked and enabled for remote access and monitoring. However, this greater interconnectivity also widens the potential attack surface for cyberthreat actors. Traditionally isolated control systems suddenly face new risks as they are connected to enterprise networks and the Internet. New access points and communications channels are opened that malicious actors can attempt to exploit to penetrate industrial environments. Without proper cybersecurity safeguards, increased connectivity essentially provides more opportunities for adversaries to infiltrate OT networks and potentially access critical manufacturing or processing systems. This interconnectivity is crucial for Industry 4.0 capabilities but needs to be managed carefully to avoid enabling cyber-attacks that can disrupt operations or damage physical assets if defenses are insufficient [23]. The growth of the Industrial Internet of Things (IIoT) is leading to more industrial devices like sensors, instruments, controllers, and appliances being connected and becoming IP-enabled [24]. However, many legacy industrial devices were designed without basic security features in mind to protect these connections [25]. Integrating newer IoT sensors with older supervisory control and data acquisition (SCADA) systems creates vulnerabilities if the security is not properly addressed [26]. The increased connectivity expands the attack surface that malicious actors could exploit. Legacy industrial systems lack modern authentication, encryption, and security monitoring capabilities. As more IIoT devices are integrated, steps need to be taken to isolate and secure both the legacy and new systems to prevent adversaries from leveraging these vulnerabilities to attack the broader industrial control system. Companies need to perform risk assessments and develop comprehensive cybersecurity strategies to safeguard IIoT and legacy devices. The convergence of IT and OT brought about by Industry 4.0 means that operational technology environments now incorporate many of the same types of common devices, protocols, and architectures used in IT for years. This includes the adoption of commercial off-the-shelf (COTS) hardware like PCs, servers, and networking equipment in industrial settings. Legacy OT systems are also being retrofitted to connect to IT networks. As a result, OT is now facing threats familiar to IT for a long time, like malware, phishing attacks, ransomware, and the remote exploitation of known vulnerabilities. These IT-oriented risks pose new challenges for industrial cybersecurity teams accustomed to more proprietary and isolated OT environments.