Industrial Cybersecurity & OT Risk worked example

Firewall Rule Review Load at 25% owner follow up and change allowance: a worked example

This worked example runs the firewall rule review load numbers for a tougher week than the baseline: 25% owner follow up and change allowance instead of the typical 35%. Estimate labor time for reviewing industrial firewall rules, zone conduits, and approved OT communication paths.

The inputs for this scenario

  • Industrial firewall rules to review: 640 rules (held at the documented default)
  • Firewall rule review rate: 28 rules / hr (held at the documented default)
  • Owner follow up and change allowance: 25 % (the input this scenario stresses; the baseline uses 35)

Working through the calculation

  • The calculation starts from the formula this tool documents: Base firewall rule review time = industrial firewall rules to review รท firewall rule review rate.
  • Required firewall rule review time works out to 28.57 hr at these inputs, and this is the headline figure for the scenario.
  • Base firewall rule review time works out to 22.86 hr at these inputs.
  • Owner follow up and change allowance works out to 25 % at these inputs.
  • Firewall rule review rate works out to 28 pieces / min at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where owner follow up and change allowance sits at 35% and the headline result is 30.86 hr, this scenario comes in 7.41% below the baseline at 28.57 hr.
  • Use it when scoping an annual firewall rule recertification or a post-segmentation cleanup, before committing staff or maintenance windows. A result at this level usually justifies acting on the stressed input before touching anything else, because every other figure in the table is downstream of it.

Results at a glance

  • Required firewall rule review time: 28.57 hr (headline result)
  • Base firewall rule review time: 22.86 hr
  • Owner follow up and change allowance: 25 %
  • Firewall rule review rate: 28 pieces / min

Run it with your numbers

  • To rerun this with your own numbers, open the live Firewall Rule Review Load calculator, set owner follow up and change allowance to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.