A Web Application Firewall (WAF) sits between your users and your app, analyzing HTTP/HTTPS traffic and blocking malicious activity. Unlike traditional firewalls, WAFs focus on application-layer attacks like SQL injection, XSS, RCE, and bots.
If you're looking for a free or open source WAF to protect your web services, here’s a practical comparison of 7 popular options—self-hosted or cloud, with or without UI, and various protection capabilities.
Comparison Overview
| WAF | Self-Hosted | Web UI | Anti-Exploit | Deploy Type | Anti-Bot | Rate Limiting |
|---|---|---|---|---|---|---|
| Cloudflare | ❌ | ✅ | ❌ | Reverse Proxy | ✅ | ✅ |
| SafeLine WAF | ✅ | ✅ | ✅ | Reverse Proxy | ✅ | ✅ |
| ModSecurity | ✅ | ❌ | ✅ | SDK | ❌ | ❌ |
| NAXSI | ✅ | ❌ | ✅ | Nginx Module | ❌ | ❌ |
| OpenAppSec | ❌ | ✅ | ✅ | SDK | ❌ | ✅ |
| BunkerWeb | ✅ | ✅ | ❌ | Nginx Module | ❌ | ❌ |
| Haltdos WAF | ✅ | ✅ | ✅ | Nginx Module | ❌ | ✅ |
Cloudflare WAF
Cloudflare’s WAF is cloud-based and fully managed. It protects your site using real-time rulesets, rate limiting, bot management, and more. It's simple to use, but not self-hosted, and its exploit-level protection may be limited unless you pay.
SafeLine WAF
SafeLine is a modern self-hosted WAF that offers a full-featured web UI, strong anti-exploit capabilities, and built-in bot protection.
It protects against:
-
SQL injection,XSS,RCE,OS command injection,CRLF,LDAP,XPath,XXE,SSRF,Path Traversal, and more -
Brute-force,HTTP Flood,Backdoor,Bot abuse
It's open source and ideal for developers looking for a production-grade WAF they can fully control.
ModSecurity
ModSecurity is one of the oldest and most widely adopted open-source WAF engines. But technically, it's just a rule engine—it doesn't have a UI, centralized log system, or full dashboard.
Often used with the OWASP Core Rule Set (CRS), ModSecurity is powerful but not user-friendly out of the box.
NAXSI
NAXSI stands for Nginx Anti XSS & SQL Injection.
It’s a lightweight Nginx module using simple rules to detect common attacks. However, the project is no longer maintained and is now archived.
Use with caution for learning purposes, but not recommended for production.
BunkerWeb
BunkerWeb is a self-hosted security wrapper around NGINX that adds useful defaults for safer web deployments. It includes a clean Web UI and supports plugin-based extensions, but lacks deep exploit and bot protections.
OpenAppSec
Backed by Check Point, open-appsec uses machine learning to detect threats in real-time by modeling normal user behavior and flagging anomalies.
It's more geared towards APIs and modern apps, supports SDK-based deployment, and integrates with cloud-native environments.
Haltdos WAF
Haltdos WAF CE is a free version of Haltdos’s commercial product. It’s built for performance, supports advanced rate limiting, anomaly detection, CAPTCHA, and traffic blocking.
Unlike legacy rule-based WAFs, Haltdos focuses on intelligent request processing and multi-layered defense.
Final Thoughts
Choosing the right WAF depends on your stack, security needs, and whether you prefer managed or self-hosted solutions.
If you want:
- Zero setup, no infrastructure → Try Cloudflare
- Full control & GUI → Go with SafeLine
- Minimalist rules-only → Use ModSecurity
- Cutting-edge ML → Try OpenAppSec
Don’t leave your web app exposed. Even a basic WAF can block thousands of automated attacks daily.
Top comments (0)