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Top 10 Free WAFs (Web Application Firewalls) for 2024

Modern web applications are constantly under attack from various threats. These threats span from well-known XSS and SQL injection attacks to newer and more sophisticated DDoS and zero-day attacks. If an attacker succeeds, the repercussions for organizations can be severe and leave lasting damage to your reputation.

26% of all web application attacks involve breaches, and WAF solutions act as a digital gatekeeper for your application, continuously monitoring incoming traffic and blocking potential issues. However, selecting a reliable WAF solution is challenging since each tool has unique standout features.

This article will give you a better understanding of the types of WAF solutions, their benefits, and the top ten WAF solutions for 2024.

What is a Free WAF Solution?

A Web Application Firewall (WAF) is a security solution that protects web applications from common cyber threats like cross-site forgery, cross-site scripting, file inclusion, and SQL injection.

A WAF operates at the application layer, unlike traditional firewalls that operate on network security. It continuously monitors incoming traffic based on a defined rule set and blocks any malicious requests before they reach your application.

Types of WAF Solutions

  • Network-based WAF: Deployed at the network perimeter. Inspects traffic before it reaches your web application.

  • Host-based WAF: Deployed directly on the web server. Monitors traffic at the server level.

  • Cloud-based WAF: Hosted and managed by third-party cloud security providers.

Benefits of Free WAF Solutions

Using a WAF solution can offer several advantages:

  • Most of the WAFs are free or offer a free version.

  • Allows customization and community-driven development.

  • Preemptive attack blocking.

  • Renowned for “install and forget” simplicity.

Key Features to Look For in a WAF Solution

When evaluating a WAF solution, consider the following key features:

  • Ability to identify and block threats before they reach your application.

  • Machine learning capabilities.

  • Rules and policy customization.

  • Ease of integration with your existing tech stack and development tools.

  • Logging and reporting features to monitor and analyze traffic.

Top 10 Free WAF Solutions for 2023

1. NGINX ModSecurity

NGINX ModSecurity is an open-source WAF solution that protects your website from cyber threats like SQL injection, remote code execution, and cross-site scripting. However, NGINX ModSecurity went End-of-Sales as of April 1, 2022, and will transition to End-of-Life effective March 31, 2024.

Main features:

  • Real-time traffic analysis for immediate threat detection.

  • Comprehensive protection using the OWASP Core Rule Set.

  • Seamless integration with NGINX.

  • Benefits from an active and supportive community.

Best for: Preventing common vulnerabilities like SQL Injection and XSS.


2. open-appsec

open-appsec is an open-source security solution that provides ML-based threat protection for web apps & APIs. It is the only WAF that preemptively blocked Log4Shell, Text4Shell, Spring4Shell, and WAF bypass attacks. Unlike competitors that are signature-dependent, open-appsec blocks zero-day attacks preemptively without signatures.

Main features:

  • Prevents OWASP Top 10 and zero-day threats automatically using the ML engine.

  • Continuous monitoring ensures your web applications are always protected.

  • Easy integration with Kubernetes, NGINX, GraphQL, HELM, and more.

  • Automatically stops and blocks malicious requests.

  • Protects against over 2,800 Web CVEs based on award-winning NSS-Certified IPS.

  • Excellent ModSecurity alternative in light of its EoL.

Best for: Protection against OWASP-Top-10 and zero-day attacks.


3. Naxsi

Naxsi is an open-source, high-performance web application firewall that’s compatible with any version of NGINX. By default, Naxsi blocks requests with URIs that exhibit patterns commonly associated with website vulnerabilities. For example, <, | or drop are not supposed to be part of a URI.

Main features:

  • Supports auto-learning to generate whitelisting rules.

  • Lightweight and resource-efficient.

  • Easily integrated with NGINX.

  • Suitable for straightforward deployments.

Best for: Choosing a WAF that’s compatible with NGINX, in light of ModSecurity’s EoL.

4. WebKnight

WebKnight is a popular WAF solution for IIS, designed for small to medium-sized businesses. Its customizable rules and anomaly detection features, make it an attractive option for organizations seeking cost-effective protection.

Main features:

  • Customizable rule sets for precise threat prevention.

  • Anomaly detection to identify unusual patterns.

  • Real-time traffic analysis.

  • User-friendly interface.

  • Tailored for smaller organizations.

Best for: Protection against buffer overflow, SQL injection, directory traversal, and character encoding.

5. CloudFlare


CloudFlare is a globally trusted web security and performance platform. It uses ML to create rule sets that defend your website from emerging attacks, like zero-day threats. You can also define customized rules based on your business requirements.

Main features:

  • Real-time threat intelligence.

  • DDoS protection.

  • Seamlessly integrates with CloudFlare's CDN.

  • Monitors and blocks the use of exposed credentials.

  • Provides analytical tools to gain insights into web traffic and threats.

Best for: Real-time threat intelligence and analytics, thanks to the easy-to-use dashboard.

Pricing: CloudFlare offers 4 pricing options: Free, Pro, Business, and Enterprise.


6. Coraza


With Coraza WAF, you can enforce policies using OWASP Core Rule Set or create your own. It’s an extensible WAF that enables customizable functionalities, features, and improvements. They recently released Coraza v3, featuring a few updates.

Main features:

  • High-quality documentation is available.

  • Supports integrations to deploy it as an application server, container, and more.

  • Scalable to support large websites.

  • Customizable policies.

Best for: A community project with a clear continuous development roadmap.


7. Shadow Daemon



Shadow Daemon has three algorithms to identify malicious requests: blacklist, whitelist, and integrity (which compares cryptographically secure checksums of the executed script to rules that specify what the checksums should be).

Main features:

  • Supports applications written in Python, PHP, and Perl.

  • Demo included to support new users.

  • Native flood protection.

  • “Install and forget” security system.

Best for: Intercepting requests at the application level, not the protocol level.


8. Vulture


The Vulture Project is a Linux WAF that blocks malicious traffic. It has an AI-powered engine for advanced threat detection, and it maintains high performance by distributing traffic to various nodes of the cluster.

Main features:

  • AI and ML engines can be added to your existing network product or solution.

  • Caching and compression function.

  • As well as the free WAF, Vulture provides some algorithms for free.

Best for: Offers the flexibility to authenticate users in line with IAM best practices.


9. IronBee



Created by Qualys as an alternative to ModSecurity, IronBee is an open source project designed for real-time monitoring and defense. While the project is small, it leverages Qualys’ stature and reliability in the cybersecurity industry.

Main features:

  • Well-commented source code.

  • Customizable WAF rules.

  • Modular architecture is straightforward, even for users not familiar with IronBee architecture.

  • Multiple deployment models, including passive and embedded.

Best for: The project has a culture of contribution, enabling information sharing for WAF best practices.


10. Lua-resty-WAF

Lua-resty-waf uses the NGINX Lua API and mimics the ModSecurity Custom Ruleset, plus there are a few additional rules. At the moment, the project has been abandoned, but there’s hope to revive it in the future.

Main features:

  • Built using the OpenResty stack.

  • Designed with speed and scalability in mind.

  • Patchset for emerging threats.

  • Easy implementation without the need to learn a new rule syntax.

Best for: Max speed of 15,000 requests per second matches CloudFare’s paid WAF.

 

open-appsec is an open-source project that builds on machine learning to provide pre-emptive web app & API threat protection against OWASP-Top-10 and zero-day attacks. It simplifies maintenance as there is no threat signature upkeep and exception handling, like common in many WAF solutions.


To learn more about how open-appsec works, see this White Paper and the in-depth Video Tutorial. You can also experiment with deployment in the free Playground.




Experiment with open-appsec for Linux, Kubernetes or Kong using a free virtual lab

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