Network Engineering
Firewall Rule Analyzer
Enter firewall rules to check for wildcard source/destination, evaluation order conflicts, missing implicit deny, and common security misconfigurations.
Calculations run locally in your browserTool
About this tool
Firewall Rule Analyzer
The Firewall Rule Analyzer checks rule sets for wildcard sources/destinations, evaluation order conflicts, shadowed deny rules, and missing implicit deny-all.
• Audit firewall rules for 0.0.0.0/0 source before a security review
• Check whether a deny rule is shadowed by an earlier allow rule
• Verify that an implicit deny-all is effective at the end of a ruleset
• Detect unnecessarily broad port ranges in a firewall configuration
Next step
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FAQ
What does this tool tell you?
The Firewall Rule Analyzer checks rule sets for wildcard sources/destinations, evaluation order conflicts, shadowed deny rules, and missing implicit deny-all.
What affects the result most?
Rule evaluation order: first-match-wins (iptables, pf) vs last-match-wins (legacy ACLs). Allow/deny logic: explicit allow required; implicit deny-all at end is best practice. Source/destination validation: 0.0.0.0/0 matches everything — flag for review.
How should I use the result?
Treat the tool's output as a first-pass check, not a proof of correctness. A clean pass means no issues in the patterns this tool recognizes; a failure points to a specific problem you can investigate in your source. The underlying spec is the authoritative source for edge cases.