Most teams use virtual patching as a comfort blanket.

In OT, you often cannot patch immediately. Uptime commitments, safety certification, vendor approvals, and fragile legacy stacks make “just patch it” unrealistic.

Virtual patching can be a smart short-term control, but only if you treat it like a bridge, not a destination.

What it actually reduces:
– Exploitability of known vulnerabilities by blocking specific traffic patterns or behaviors
– Exposure window while you coordinate downtime, testing, and vendor support

What it does not fix:
– The vulnerable code still exists
– Local exploitation paths, misconfigurations, and unknown variants may remain
– Asset and protocol blind spots can turn into false confidence

Disciplined virtual patching looks like:
1) Define an expiration date and an owner (when does “temporary” end?)
2) Specify coverage: which CVEs, which assets, which protocol functions, which zones
3) Validate with proof, not assumptions: replay exploit attempts, run vulnerability scans where safe, confirm logs/alerts, verify rule hit rates
4) Run a parallel plan to remove it: patch path, compensating controls, maintenance window, rollback plan
5) Reassess after changes: new firmware, new routes, new vendors, new threats

If you can’t explain what your virtual patch blocks, how you tested it, and when it will be removed, you have not reduced risk. You’ve created permanent temporary security.

How are you validating virtual patching effectiveness in your OT environment?