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Application & OT Security · Intermediate

Unidirectional Gateway

A hardware-enforced network device that allows data to flow in only one direction, typically from OT out to IT.

Definition

Also known as a data diode, it physically prevents any inbound traffic to a protected network while software replicates data (such as historian records) outward. It is stronger than a firewall because it cannot be misconfigured to allow inbound sessions.

Example

Plant data flows through a data diode to a corporate replica historian; nothing can be sent back into the plant.

Exam tip

Data diode = physical one-way flow; ideal for protecting critical control zones.

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