Programmable Logic Controller
Also known as:PLC
Programmable Logic Controller: Industrial computer that cyclically reads sensor values and derives actuator commands for a process. The PLC is the workhorse of operational technologyOperational TechnologyHardware and software used to monitor or control physical equipment, machinery, and industrial processes. and drives physical processes directly.
How it works and where it fits
A PLC runs a fixed cycle: read inputs, execute the program, write outputs. It is programmed in the IEC 61131-3 languages, such as ladder logic or structured text, through engineering software. That programming path is precisely what matters for security, because it permits overwriting the control logic during operation. Historically many devices have no authentication for it, only a key switch for changing operating mode.
Practical security relevance
An attack on a PLC rarely targets data but the physical process: altered setpoints, manipulated limits, overwritten logic, or a forced stop. Because availability takes priority, active scans and vulnerability tests in production are risky and generally belong in a coordinated test environment. Hardening means strictly limiting programming access, controlling the mode switch, inventorying firmware levels, and logging changes to control logic.
Related concepts
- Operational TechnologyOperational TechnologyHardware and software used to monitor or control physical equipment, machinery, and industrial processes.: Hardware and software used to monitor or control physical equipment, machinery, and industrial processes.
- SCADASCADAControl system for monitoring and operating geographically distributed industrial processes.: Control system for monitoring and operating geographically distributed industrial processes.
- Operational Technology SecurityOperational Technology SecurityProtects industrial control, production, and process control systems.: Protects industrial control, production, and process control systems.
- Firmware SecurityFirmware SecurityProtects low-level software, boot processes, and hardware functions from tampering.: Protects low-level software, boot processes, and hardware functions from tampering.