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ModSecurity

modsecurity.org

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Spec score 7.6 #10 of 27 in Website Security Software

What it is

ModSecurity is an open-source web application firewall that examines incoming HTTP(S) traffic and can block malicious requests before they reach an application. It runs inside Apache, Nginx or IIS as a module, not as a separate appliance or proxy. The project provides traffic visibility, a rules language and an API for implementing protections. ModSecurity can run alone or with the OWASP Core Rule Set, which the FAQ says provides broad coverage against common web attacks. Listed uses include real-time security monitoring and access control, HTTP traffic logging, passive security assessment and web application hardening. It supports Linux, Unix-like systems, Windows and macOS when paired with a compatible web server. Installation guidance recommends starting in detection-only mode, reviewing and tuning events, then enabling blocking. Inspecting every request can have a small performance impact, and tuning rules can help manage it. OWASP maintains the project with community contributors, with Slack and GitHub listed for community activity. The plan costs nothing; managed rule sets are not included.

Spec sheet

Purpose
ModSecurity is an open-source, rule-based web application firewall that analyzes incoming traffic and helps block malicious requests before they reach an application.Read 4 Oct 2026 · modsecurity.org
Deployment
The FAQ says ModSecurity runs inside a web server rather than as a standalone appliance or proxy.Read 4 Oct 2026 · modsecurity.org
Community
The project directs users to Slack and GitHub for community discussions and projects and says it welcomes contributors and developers.Read 4 Oct 2026 · modsecurity.org
Maintenance
The FAQ says ModSecurity is maintained by OWASP with support from a wider community of contributors.Read 4 Oct 2026 · modsecurity.org
Performance
The FAQ says inspecting every incoming request can have a small performance impact and that tuning rules can help keep the site running smoothly.Read 4 Oct 2026 · modsecurity.org
Recent security fixes
A September 2026 security update digest describes fixes in ModSecurity 2.9.15 and libmodsecurity 3.0.17 for multiple reported issues.Read 4 Oct 2026 · modsecurity.org
Rule sets
ModSecurity can run on its own or with the OWASP Core Rule Set, which the FAQ says provides broad coverage against common web attacks.Read 4 Oct 2026 · modsecurity.org
Supported operating systems
The FAQ lists Linux, Unix-like systems, Windows, and macOS when paired with a compatible web server.Read 4 Oct 2026 · modsecurity.org
Traffic inspection
The project describes ModSecurity as a cross-platform WAF module that provides visibility into HTTP(S) traffic and a rules language and API for implementing protections.Read 4 Oct 2026 · modsecurity.org
Tuning
The installation guide recommends starting in detection-only mode, reviewing and tuning events, and then enabling blocking.Read 4 Oct 2026 · modsecurity.org
Usage scenarios
The project lists real-time application security monitoring and access control, full HTTP traffic logging, continuous passive security assessment, and web application hardening as usage scenarios.Read 4 Oct 2026 · modsecurity.org
Web server integrations
ModSecurity can be installed as a module for Apache, Nginx, or IIS.Read 4 Oct 2026 · modsecurity.org

Plans and prices

ModSecurity Free Open-source WAF engine · runs as a module inside a web server Read 4 Oct 2026 · modsecurity.org

Every ModSecurity plan and price →

Strong points and limits

Strong points

  • Runs as a module for Apache, Nginx or IIS
  • Can log full HTTP traffic
  • Supports detection-only operation before blocking
  • Works with the OWASP Core Rule Set

Limits

  • Requires a compatible web server
  • Request inspection can have a small performance impact
  • Managed rule sets are not included

Who it suits

ModSecurity suits administrators who want to inspect and control web traffic within an Apache, Nginx or IIS server. It can run independently or alongside the OWASP Core Rule Set.

Verdict

ModSecurity offers traffic inspection and rule-based protection inside a compatible web server. Administrators should tune rules before enabling blocking and account for the potential performance impact.

Where Specifiction places it

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