Industrial Cybersecurity & OT Risk worked example

Firewall Rule Review Load at 40% owner follow up and change allowance: a worked example

This scenario runs the firewall rule review load calculation on the strong side: 40% owner follow up and change allowance, with every other input held at its documented default. Use it when preparing rule recertification, segmentation audits, or change window planning.

The inputs for this scenario

  • Industrial firewall rules to review: 640 rules (unchanged)
  • Firewall rule review rate: 28 rules / hr (unchanged)
  • Owner follow up and change allowance: 40 % (raised for this scenario; the documented default is 35)

Working through the calculation

  • Applying the documented formula (Base firewall rule review time = industrial firewall rules to review รท firewall rule review rate) to the inputs above produces each figure below.
  • At this operating point the engine returns 32 hr for required firewall rule review time, the number this scenario is built around.
  • At this operating point the engine returns 22.86 hr for base firewall rule review time.
  • At this operating point the engine returns 40 % for owner follow up and change allowance.
  • At this operating point the engine returns 28 pieces / min for firewall rule review rate.

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 3.7% above the baseline at 32 hr.
  • Use it when scoping an annual firewall rule recertification or a post-segmentation cleanup, before committing staff or maintenance windows. Treat this as a target state: the delta against the baseline quantifies what the improvement is worth before you commit to chasing it.

Results at a glance

  • Required firewall rule review time: 32 hr (headline result)
  • Base firewall rule review time: 22.86 hr
  • Owner follow up and change allowance: 40 %
  • Firewall rule review rate: 28 pieces / min

Run it with your numbers

  • Every input above is editable in the live Firewall Rule Review Load calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.