Secure Remote Access in OT: Why Direct Vendor VPNs Become a Production Risk
In a plant where every vendor connects through its own VPN, the real access model is usually much wider than anyone thinks.
The symptom on site
Vendors and integrators connect through parallel VPNs, jump hosts or temporary tools. Nobody can say clearly who connected, when, and to what.
Likely root cause
Access paths were opened one at a time as needed, never closed, and never tied to a zone design. Nobody owns the path from the internet to the PLC/SCADA layer.
What to check
Is there a list of active remote access paths? Which vendor can reach which system? Are sessions logged? Are maintenance windows defined? Is there a written emergency access rule?
The wrong fix
Approving each vendor tool one by one without a zone diagram or access matrix.
A better approach
Define the zone/conduit structure, approved remote paths, logging expectations and vendor session limits tied to maintenance windows.
Our view
We treat remote access as OT architecture designed around production continuity — not as a product installation.
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