What is the Purdue model, and why does cross-level traffic matter?
The Purdue model is a reference layout that sorts a plant's systems into levels: the physical process and its sensors at the bottom, controllers above them, then supervisory systems such as HMIs and SCADA, then site operations such as the historian and production planning, and the business network at the top. The rule that matters is that each level talks mainly to its neighbours, and that traffic between business and production passes through a controlled boundary, usually a DMZ. Traffic that jumps levels, such as an office PC talking straight to a PLC, is either a design mistake or something an attacker is using, and it is one of the clearest warning signs in OTOT: operational technology. The computers that run machines, production lines, building systems and utilities.. Many real plants do not fit the model neatly, which is fine; what matters is that you know which crossings are intended. From the Pro plan, NetSenX flags traffic that crosses Purdue levels, from passive capture.
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Terms used here
- OT (operational technology)
- The computers that run machines, production lines, building systems and utilities.