ModSecurity
Open-source web application firewall for Apache, Nginx, and IIS
ModSecurity is a free WAF engine that detects and blocks malicious HTTP requests. Operates as a module for major web servers to protect against OWASP Top 10 attacks and custom threats.
ModSecurity provides real-time HTTP traffic analysis and filtering with rule-based threat detection. Deploys as a module within Apache, Nginx, or IIS to inspect requests before they reach applications. Includes OWASP Core Rule Set for common vulnerabilities, supports custom rules, and offers both blocking and monitoring modes. Self-hosted, no vendor lock-in.
Pros
- Deploy on-premises with full control and visibility
- Use industry-standard OWASP Core Rule Set or create custom rules
- Inspect request/response payloads, headers, and cookies in real-time
- Free and open-source with active community support
Cons
- Requires server-level integration and maintenance expertise
- Rule tuning needed to avoid false positives in production
- No built-in DDoS rate-limiting or volumetric attack mitigation
Best For
DevOps teams and system administrators running self-managed web servers who need application-layer protection without managed WAF costs.
Pricing
Free Forever
- Core features included
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