Operational Technology (OT) security safeguards the industrial systems, networks, and physical processes that power modern society. Unlike Information Technology (IT), which prioritizes data confidentiality, OT security focuses on the availability, reliability, and safety of physical operations, protecting the technology behind turbines, robotic arms, pumps, and pipeline valves. As Industry 4.0 drives the convergence of these traditionally isolated systems with enterprise networks, cyber resilience must account for equipment designed to run continuously for decades, far longer than the rapid refresh cycles of the IT world. What is OT (operational technology) security? Operational Technology (OT) refers to hardware and software that monitors or controls physical processes, from chemical reactions to mechanical production lines. OT security protects these systems from cyber threats that could disrupt operations, damage equipment, or endanger human safety. The OT domain uses specialized terminology reflecting its hierarchical control structure: • Industrial Control Systems (ICS): The command centers for processes ranging from automotive assembly to water treatment. • SCADA (Supervisory Control and Data Acquisition): Systems that monitor and control geographically dispersed assets, such as regional power grids or pipeline networks. • PLCs (Programmable Logic Controllers): Ruggedized, real-time computers that automate specific functions, like regulating pressure in a chemical reactor. • HMIs (Human-Machine Interfaces): The screens and consoles operators use to visualize and interact with process data. • MES (Manufacturing Execution Systems): Software that aligns plant floor operations with business goals and production schedules. These systems prioritize determinism, the guarantee that a command will execute within a specific timeframe. In OT environments, latency is a physical hazard: a delayed signal can cause mechanical failure or endanger personnel. The scale of industrial connectivity is expanding rapidly. According to IoT Analytics, the number of connected IoT devices reached approximately 21.1 billion by mid-2025, up from 18.5 billion in 2024, with projections approaching 39