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Open Source WAF / WAF Engine / Rule-based WAF

ModSecurity WAF

ModSecurity is a widely known open-source WAF engine and a common baseline for rule-based web application firewall deployments.

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Pricing
Free
License
Open source
Deployment
Nginx, Apache, IIS, Reverse Proxy
Integrations
OWASP CRS, Nginx, Apache
Last checked
2026-05-30

Best fit

  • Rule-based detection
  • Existing CRS users
  • Legacy WAF stacks

Potential limitations

  • Rule tuning can be noisy
  • Operational complexity depends on connector and rule set quality

WAFWiki read

Long-running open-source WAF engine.

This profile is written for evaluation rather than promotion. Use it to understand where ModSecurity fits, which assumptions need validation, and which alternatives deserve side-by-side testing.

Evaluation checklist

  • Verify current pricing and license terms on the official site.
  • Confirm deployment path against your production topology.
  • Test false positives with real application traffic before rollout.
  • Document rollback, logging, and alert routing before enabling blocking mode.

Feature snapshot

ModSecurity capabilities to verify

Transaction inspectionRule engineCRS ecosystem

Comparisons

ModSecurity alternatives and versus pages

SafeLine vs ModSecurityModSecurity vs CorazaF5 WAF for NGINX vs ModSecurity

ModSecurity reviews

ModSecurity Review

ModSecurity tutorials

ModSecurity with NGINX and OWASP CRS Setup Guide

FAQ

What is ModSecurity best for?

ModSecurity is commonly evaluated for Rule-based detection, Existing CRS users, Legacy WAF stacks.

Is ModSecurity free?

ModSecurity pricing path: Free. Always verify current pricing on the official website.

Sources