Topic starter
25/10/2026 10:59 am
TL;DR: 51% of organisations had incidents involving legacy Windows systems in the past 12 months, TXOne Networks found in survey data. OT operators need protection that works around uptime limits and the deployment friction that still slows defensive change.
Editorial analysis by NHI Mgmt Group, based on content published by TXOne Networks: “The Legacy OT Dilemma Part 2: The 2026 Update”.
By the numbers:
- 51% of organisations experienced cybersecurity incidents involving legacy Windows systems in the past 12 months, up from 43% in 2025.
- One in six say more than 75% of their operational infrastructure depends on legacy Windows.
Key questions
Q: Why do legacy Windows systems increase operational risk in industrial environments?
A: They extend the lifespan of unsupported software inside environments where uptime, compatibility, and vendor dependencies make fast remediation difficult.
A: A common mistake is assuming firewalling and log analysis are enough for OT.
Q: What breaks when legacy Windows is still running in OT environments?
A: What breaks is the assumption that standard enterprise patching, endpoint enforcement, and upgrade cycles can be applied without operational impact.
Practitioner guidance
- Map every legacy Windows asset to operational criticality Build a current inventory of Windows-based OT hosts, then classify which systems are essential to production, which are partially replaceable, and which can only be protected in place.
- Prioritise zero-disruption controls for production systems Require proof that any endpoint or network control can deploy without modifying the system, without maintenance windows, and without interrupting OT applications.
- Coordinate segmentation and endpoint coverage Align network inspection, segmentation policy, and host protection around the same asset map so no legacy platform sits in an unmonitored seam.
Bottom line: Legacy Windows remains deeply embedded in OT, so unsupported systems must be governed as a long-term exposure rather than a temporary exception.
Glossary terms: Legacy Windows Systems, Zero-disruption security, OT control seam risk, Compensating Control
Explore further
View Full Forum → | NHI Foundation Course → | Our Services → | Read the full analysis →
This topic was modified 7 days ago by NHI Mgmt Group
27/10/2026 7:16 pm
Legacy Windows in OT is now a standing governance problem, not a temporary technical exception. Industrial operators are still running systems that support production but sit outside normal patch and upgrade assumptions. That means security programmes have to govern unsupported platforms as enduring assets, with compensating controls that acknowledge operational continuity. The practical conclusion is that legacy risk management belongs in architecture and governance, not in one-off remediation projects.
A question worth separating out:
Q: How should organisations balance legacy replacement with protective controls?
A: They should stop treating replacement and protection as mutually exclusive. The article shows many operators now see dedicated protection as cheaper than immediate replacement, which makes sense when equipment, downtime, and support constraints are factored in. The right approach is to protect the installed base while sequencing replacement based on risk and criticality.
👉 Read our full editorial: Legacy Windows risk is deepening across European OT environments
This post was modified 7 days ago by NHI Mgmt Group