Firewall Rule Tester Calculator

Firewall Rule Test Inputs

Example Data Table

Formula Used

This tester uses deterministic firewall matching and a weighted diagnostics score. A rule matches only when every required condition passes.

Rule Match Score = (Sum of passed condition weights / 100) × 100

Weights prioritize protocol, source and destination CIDR, ports, schedule, and state. The score helps identify near-matches when a packet fails one or two checks.

Exposure Risk Score increases for broad allows, ANY protocol, ANY destination port, disabled logging, risky service ports, and ingress exposure.

How to Use This Calculator

1. Enter the firewall rule settings, including CIDR, protocol, ports, direction, interface, zone, and schedule.
2. Enter packet details you want to test, such as source and destination IPs, ports, protocol, and timestamp.
3. Click Test Rule to evaluate the packet against the rule.
4. Review the result panel above the form for the verdict, match score, exposure risk, and conflict indicator.
5. Use the condition table to see exactly which checks passed or failed.
6. Download CSV or PDF reports for audit notes, troubleshooting logs, or policy review records.

Tip: Use ANY for wildcard matching in protocol, CIDR, ports, direction, interface, zone, or weekdays.

Rule Validation Coverage

Firewall testing improves reliability by measuring whether packet attributes align with rule intent before deployment. This calculator evaluates protocol, source and destination CIDR, source and destination ports, direction, interface, zone, state, weekday, and time window in one pass. Using weighted checks reduces blind spots during reviews, because analysts can see partial matches, not only binary outcomes, when validating segmentation rules or troubleshooting access tickets.

Match Score Interpretation

The match score is a weighted percentage that summarizes rule alignment with observed packet data. In practice, scores above 90% usually indicate one minor mismatch, such as zone naming or state tracking. Scores between 70% and 89% often reveal policy drift after network changes. Lower scores indicate mis-scoped rules, incorrect CIDR boundaries, or protocol and port assumptions that no longer match production traffic patterns.

Port and Protocol Risk Patterns

Risk scoring complements the match result by highlighting exposure characteristics. Broad allow rules, ANY protocol entries, wildcard destination ports, and disabled logging increase operational risk. The calculator also raises risk for sensitive service ports such as SSH, SMB, RDP, database ports, and ingress traffic. Teams can use this score during change approvals to compare alternative rules and prefer narrower conditions with stronger observability and auditability.

Scheduling and Change Control

Time windows and weekday constraints are frequently omitted in fast change cycles, yet they significantly reduce attack surface for temporary access. This calculator tests same-day and overnight schedules, then verifies weekday lists against packet timestamps. Security teams can simulate contractor access, maintenance windows, and incident response exceptions before enabling rules. Documented test results also support separation-of-duties reviews and post-change validation in regulated environments.

Audit Reporting Value

Exportable CSV and PDF outputs turn a single rule test into evidence for operations and compliance teams. Summary metrics capture verdict, priority, logging status, conflict indicators, and exposure risk, while condition tables show exactly which checks passed or failed. This format helps analysts reproduce outcomes, compare revisions, and attach proof to change requests, quarterly firewall reviews, or remediation plans after internal security assessments. Organizations often baseline monthly pass rates, exception counts, and high-risk rule percentages, then track reductions after cleanup projects to demonstrate measurable policy hardening.

Frequently Asked Questions

1) What does a “NO MATCH” result mean?

It means at least one required condition failed. Check the condition table to identify whether the mismatch came from CIDR, ports, protocol, state, direction, zone, or schedule.

2) Can I test temporary maintenance rules?

Yes. Use the weekday and time window fields to simulate maintenance access. The calculator supports normal business windows and overnight windows crossing midnight.

3) Why is the match score high when the verdict is no match?

A high score with no match usually means one critical field failed while most others passed. This helps identify near-matches and rule drift quickly.

4) How is the exposure risk score useful?

It flags broad or risky rule characteristics, such as ANY protocol, wildcard ports, ingress exposure, sensitive service ports, or disabled logging, so reviewers can tighten controls.

5) Does the tester support ICMP traffic?

Yes. For ICMP packets, port checks become not applicable, and the calculator marks them as pass-by-design while still testing protocol, CIDR, direction, and schedule conditions.

6) What should I export for audit evidence?

Export both CSV and PDF. The summary captures verdict and scores, while the condition table preserves detailed pass/fail evidence for change records and reviews.