When the Purdue model was introduced in 1992 by Theodore J. Williams and the Purdue University Consortium, few other models had yet outlined a clear information hierarchy for CIM, which began to take hold of the industry in the mid-to-late 1980s.
Today, with the industrial internet of things (IIoT) blurring the line between IT and OT, experts often wonder whether the Purdue model still applies to modern ICS networks. Its segmentation framework is often set aside, after all, as data from Level 0 is sent directly to the cloud. However, many suggest it’s not yet time to discard the model.
In 2020, Litmus CEO Vatsal Shah said, “The Purdue Model still serves the segmentation requirements for both wireless and wired networks and protects the operational technology (OT) network from unwarranted traffic and exploits.”¹
SANS Institute took a similar position in 2021, saying, “Even if its hierarchical layers can no longer be uniformly applied to modern architectures, sorting ICS and IT devices and systems into distinct functional layers helps administrators and security practitioners determine where to apply security measures effectively.”²
Forbes maintained that perspective in 2022: “The Purdue Model is dead. Long live the Purdue Model.”³
Industrial uptime requirements and budgets often mean that the new can’t yet replace the old, and that holds true for the Purdue model despite the rise of IoT. Instead, many are advocating for a hybrid approach of applying macro segmentation with zero trust to overcome the unique challenges of modern ICS security.
1. AutomationWorld, “Is the Purdue Model Still Relevant?,” May 2020.
2. SANS Institute, “Introduction to ICS Security Part 2,” July 2021.
3. Forbes, “A Reimagined Purdue Model For Industrial Security Is Possible,“ January 2022.