Best Open Source Web Application Firewall to Secure your Web Apps

open source web application firewall

Are you looking for an open-source web application firewall?

ModSecurity, IronBee, NAXSI, WebKnight, and Shadow Daemon are the best open-source WAF. They are capable of protecting your web apps from malicious requests, bot attacks, and many other web threats.

There are lots of free WAF that secure your web apps at no charge. The best part of open-source WAF is the freedom to modify the coding according to your projects.

Pros and Cons of Open Source Web Application Firewall

Pros of Open Source WAF:

You should use an open-source Web App Firewall if you do not want to pay a hefty amount of sum for your web app security. 

Open source WAF also offers the freedom to webmasters and developers to apply rules as their project demands.

They can filter the requests by setting up their barricades for the traffic. You can tighten the security a lot by adding more modules to the software.

The open-source WAFs are highly flexible and customizable.

Cons of Free WAF:

You have to manage everything yourself.

Installation of the Free WAF is not straight forward all the time. With Cloudflare or other paid WAFs, you simply insert your domain name and activate the firewall.

Free WAFs do not have clear interfaces, so reading the traffic and attacks is not easy.

There are logs, but the visual presentation of data is not sleek or readable by everyone.

Most of the open-source firewalls do not support caching, which ultimately affects the page loading speed.

Open Source WAF List

The best open source WAF are:

  1. ModSecurity
  2. IronBee
  3. NAXSI
  4. WebKnight
  5. Shadow Daemon
  6. Lua-resty-waf
  7. Vulture

#1 ModSecurity


ModSecurity is indeed a beast among the open-source web application firewalls. It is well equipped with tons of features that you can enable to protect your web apps.

ModSecurity offers you complete freedom to extend the capabilities of the tool so it can fit your needs.

Moreover, the software is quick to install and start working as soon as it is installed.

Feature of ModSecurity

  • Real-time application security monitoring and access control
  • Full HTTP traffic logging
  • Continuous passive security assessment
  • Web application hardening
  • Solid documentation

The open-source community of ModSecurity is active and consistently releases updates. The free rules offered by the ModSecurity is enough to strengthen the security of the web app.

#2 IronBee

iron bee open source waf

IronBee is a framework to build a firewall.

It is made by the same team that created the ModSecurity. ModSecurity has a licensed version for commercial use, while IronBee is entirely free for operation of every scale.

The purpose of making WAF is to create a cloud-based WAF that could be affordable by everyone. IronBee serves that purpose.

Features of IronBee:

  • State-of-the-art application security inspection engine
  • Modular architecture that allows developers to add their modules
  • Highly portable and very lightweight

IronBee is still in the development phase and is not available in binary install packages though you can download the code from GitHub.


NAXSI Open Source Web App Firewall

NAXSI means Nginx Anti XSS & SQL Injection. The tool is a popular reverse proxy firewall with simple rules, to begin with. 

NAXSI does not shield the web apps from multiple attacks. But it is the best free web application software to fight against frequent attacks like Cross-Site Scripting and SQL Injection.

Every HTTP request (GET|PUT|POST only) is verified on the compliance to the patterns of accepted rules set by default in file naxsi_core. rules.

Features of NAXSI:

  • Resistance against unknown attacks with dangerous characters and expressions
  • Low memory footprint and minimum runtime processing
  • Powerful learning process
  • Easy to manage in comparison to other WAFs

NAXSI is compatible with all the Nginx versions. You hsave to download it from GitHub.

#4 WebKnight


WebKnight is an application firewall for the Microsoft IIS. The set of tools scan all the requests and filter them according to rules set by the administrator.

However, rules do not depend on past attack signatures. Instead, WebKnight uses buffer overflow, SQL injection, directory traversal, and character encoding as filtering.

The latest version of WebKnight has a web interface for the admin to add, remove and maintain the rules, and check out the statistics regarding the traffic.

Features of the WebKnight:

  • Logging all request
  • HTTP error Logging
  • SSL protection
  • Authentication scanning
  • Prevent Hotlinking
  • Web interface
  • Action per rule

WebKnight is a fantastic open-source web application firewall for the IIS web server.

#5 Shadow Daemon

shadow daemon

Shadow Daemon is a web application firewall that detects, records, and blocks attacks on web apps by filtering out malicious intent. 

It is free software, and you can modify the code to create a personal firewall. The Shadow Daemon is easy to install and only takes a few minutes.

A clear web interface makes it easy to monitor the attacks and configure the firewall setting.

Features of Shadow Daemon:

  • High coverage with multiple connectors
  • Accurate detection by combining blacklists and whitelists
  • Only block the dangerous part of the malicious requests
  • Closer to the application for the optimum security

Shadow Daemon is backed with extensive documentation and an active community.

This is an easy to use and manageable free open source web application firewall.

#6 Lua-resty-waf

Lua-resty-waf is in the development phase. It is a reverse proxy WAF built on OpenResty stack.

The tools analyze the HTTP request by using the Nginx Lua API and filter out the requests as per the flexible rules. 

However, Lua-resty-waf requires various third party resty Lua modules, but the package has packed all of them.

This open-source WAF is designed for efficiency and scalability. It leverages the Nginx asynchronous processing model to process the requests quickly.

Features of Lua-resty-waf:

  • Analyze HTTP request for anomalous behavior
  • Prevent brute force attacks
  • Real-time DNS blacklisting
  • Automatic log audit backup
  • Memcache and Redis cache for long term storing

Lua-resty-waf is a high-performance open-source, free web application firewall. The speed of processing the request of Lua is similar to Cloudflare.

#7 Vulture


Vulture is not that popular, but it is a lightweight and effective Linux WAF. It is a reverse proxy based on Apache web server.

Vulture distributes all the incoming traffic to various nodes of the cluster to enhance the performance. The process could become faster by adding more nodes to the cluster.

You can control the strictness of the security by activating the TLS, controlling the user’s reputation, and blocking various attacks.

Features of Vulture:

  • Authenticate the users and propagate their identity
  • Stream encryption
  • Application firewall based on ModSecurity
  • Caching and compression function

You can download Vulture from the download page. The latest version of the Vulture requires Modern Hypervisor and 4GB Ram.

More Open Source WAFs

These free WAFs are still available, but there are no resources and communities around them.

Be safe while installing them for them. There is no documentation on these free WAFs.

But they are a great option for experiment purposes.

Are Open Source WAF secure?

Yes, they are secure. They are as safe as you can make them.

However, it will be your responsibility to make them secure and powerful enough to protect your web app.

Yet there are many types of attacks that open-source software cannot prevent. For the better security of your business, having a premium WAF is a wise decision.

CloudFlare and Sucuri are the best premium WAF.

Premium Web Application Firewall

Paid WAF software to protect your site are:

  1. Cloudflare
  2. Imperva Incapsula
  3. Akamai Kona Site Defender
  4. F5 Silverline
  5. Amazon Web Services WAF
  6. AppTrana
  7. Sucuri
  8. Qualys WAF
  9. Barracuda
  10. Fortinet

ServerGuy is partner with the Sucuri and CloudFlare — The Best WAF of the Time.

Your brand and your customers are safe with our Hosting.

Frequently Asked Question

What WAF mean?

WAF means Web Application Firewall: It is a firewall to filter the HTTP requests coming from the internet. It works as a proactive shield between the site and the internet.

What does a WAF protect against?

WAF protects against malicious HTTP requests, bot attacks, DDoS, Malware, spammer, and hackers.

Mainly the WAF works as a shield for cross-site forgery, cross-site-scripting (XSS), file inclusion, and SQL injection.

Why do you need a WAF?

We need WAF to protect your site from many Internet attacks. These attacks can increase the load on the website or steal the data.

Web Application Firewall filter out all the requests so only the legitimate requests could get a response.

How does WAF work?

WAF acts as a protective shield between the website and the internet.

It functions as a reverse proxy that protects your server from unwanted exposure by having visitors pass through the firewall before reaching the server.

What is the difference between WAF and Firewall?

A traditional firewall safeguards the flow of data between servers during WAF filter traffic for a specific web application.

Is Cloudflare a WAF?

Cloudflare offers a range of web security services. One of these services is WAF, which is a paid function of the Cloudflare.


Installing open source WAF is an excellent choice for personal projects or projects that do not demand high-security measures.

When it comes to serious protection from internet threats, premium firewalls are the best option.

The free ones do have a limit to secure your web apps, and there is so little they can do if a serious attack starts.

However, if you have knowledge and experience of Internet Security, then you can create a powerful WAF out of any open source WAF.

Premium WAF not only gives 360-degree security to your site but also presents the data in the readable form.

The simplicity of the tool makes them preferable. It is worth investing in the security of your web site.

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