Rapid digital development has expanded the scope of cybersecurity to include critical infrastructure and cyber-physical systems, such as electricity grids, water treatment plants, industrial facilities, and transportation networks. Although the integration of Information Technology (IT) and Operational Technology (OT) improves efficiency, it also introduces security challenges that may lead to physical damage, economic disruptions, and threats to public safety. These systems face increasing risks due to the reliance of some industrial control devices on outdated protocols that lack adequate security measures, making them vulnerable to malware and attacks that manipulate operational systems. To address these challenges, adopting a defense-in-depth strategy is essential. This includes network segmentation, implementing access controls based on the Zero Trust principle, continuous system monitoring, and securing supply chains. These measures are crucial for strengthening the resilience of critical infrastructure, ensuring service continuity, and protecting lives and property in the digital society.