Glossary · Automation fundamentals, platforms and components
Compensating controls
Also known as: Compensating countermeasures
German: Ersatzmaßnahmen
In OT security, compensating controls are alternative security measures used when a component cannot meet a security requirement itself, for example network segmentation or monitoring for a legacy controller that cannot be patched. IEC 62443 uses the term compensating countermeasure.
- Automation components
- OT security
- Standards
In one sentence
Compensating controls are alternative security measures used when a system cannot meet a security requirement itself, such as segmenting a legacy PLC.
Example
Because an older HMI cannot enforce strong passwords, it is placed in a separate zone behind a firewall that only allows traffic from the engineering station.
How it applies
- Engineering: Compensating controls are chosen during risk assessment and zone and conduit design. They should address the same threat as the missing capability.
- Operation: Their effectiveness must be monitored; a firewall rule that is later opened removes the compensation.
- Documentation: Record which requirement is not met, which compensating control replaces it, why it is considered adequate and who accepted the residual risk. Operators need this in the security documentation handed over with the system.
Compensating controls vs. fixing the weakness
Compensating controls reduce risk around a weakness, they do not remove it. When the component is replaced or can be updated, the original requirement should be implemented and the compensation reviewed. Using compensating controls does not by itself make a system compliant with IEC 62443 or the Cyber Resilience Act (CRA).