An industrial controller is a device that runs control logic for machinery or process equipment. Common examples include programmable logic controllers (PLCs) and other controllers used to operate sensors, motors, valves, and production processes.
Controllers matter in cyber security because commands or configuration changes can affect physical operations, not just data. In an attack, an intruder who gains access to an operational technology network may try to alter controller logic, settings, or commands. Defenders limit this risk with network segmentation, restricted access, monitoring for unexpected changes, and tested recovery procedures.