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WAF Comparison: ModSecurity WAF vs. AWS WAF vs. open-appsec WAF

As the digital world continues to evolve, the need for secure web applications has become more important.

To address this need, organizations rely on Web Application Firewalls (WAFs) to protect against malicious attacks and threats. ModSecurity, AWS WAF and open-appsec are three popular WAF solutions offering unique features and benefits.

In this article, we will dive into the differences between these WAFs to help you understand which solution best fits your organization's security needs.

Let’s get started.

The Difference Between AWS WAF, ModSecurity WAF and open-appsec WAF


ModSecurity WAF


open-appsec WAF



Its pricing is based on the number of web Access Control List (Web ACL) and requests you receive

It is free but has a paid version for technical support.

False positives

High level

High Level

Low thanks to machine learning

Ease of use and Maintenance complexity

Beginners might find this complex to use.

It is easy to use.


Rulesets and policies

Offers a free core ruleset and a commercial ruleset.

It offers AWS rules to help you customize your web app security.

It doesn’t offer rulesets or policies; instead, it uses machine learning to offer more effective protection for your web app.

WAF community and customer service.

It has a large community.

The AWS WAF has a large community.

The open-appsec WAF is new, so it has a small community. Consequently, it doesn't take long for an admin to assist you with any issue you encounter when utilizing open-appsec.


It is an open-source solution.

It is not an open-source solution.

It is an open-source solution with a source code that a third party verified independently.

Zero-day detection



Uses machine learning to detect and prevent zero-day attacks.

Similarities Between ModSecurity WAF, AWS WAF and open-appsec WAF

Here are some similarities between the ModSecurity, AWS and open-appsec WAFs:

  1. All three WAFs analyze incoming traffic in real-time to detect and prevent malicious activity.

  2. All three WAFs generate logs of all processed requests to provide visibility into the activity on the web application and help detect potential security threats.

  3. All three WAFs provide effective protection against common web-based attacks.

  4. AWS WAF is based on ModSecurity engine

ModSecurity Web Application Firewall

ModSecurity was one of the first open-source WAFs that existed, with the first code being released over twenty years ago. It's gone through a lot of major versions over the years, and due to its open-source nature, many companies were able to implement ModSecurity for their web server applications.

The project has changed hands over the years, and the current maintainer, Trustwave SpiderLabs, has made the decision to stop supporting and maintaining the project after July 1, 2024. While the project will still be open-source, this can be an indication that it's no longer viable to work on a codebase that is this old and that SpiderLabs considers it better to move its resources elsewhere.

ModSecurity WAF Features

  • Core Rule Set

ModSecurity rulesets are divided into the core (free) and the commercial (more advanced and paid). You can use both rulesets to flexibly perform simple and complex security operations that protect your web app from attacks like XSS, SQLi, session hijacking, trojans and other exploits.

Outstandingly, when a particular rule has been triggered too often by a particular IP address, this feature permanently blocks the IP so that it doesn’t have access to your cPanel account.

  • Virtual Patching

With this ModSecurity WAF feature, you can prevent your web app from being exploited by known vulnerabilities. This feature is more valuable when you know your app vulnerabilities but can’t patch them.

In a case like this, the ModSec virtual patching uses your customization of the core ruleset to filter out attacks before they reach your application’s logic and without modifying your web app’s architecture.


  • Web Server and Application Hardening

It is easy to maintain the security status of a hardened system because it has a minimal attack surface. Because of this, the ModSecurity web application firewall hardens your web application by removing unnecessary and unused software services, closing open network ports, changing the default setting, configuring software stacks, etc.

Pros and Cons of ModSecurity WAF



It is open-source, so there’s no restriction on how you can modify and customize it.

The project is end of life.

It serves as a server module and can be deployed on different servers.

No pre-emptive zero-day protection due to use of signatures

The ModSecurity team offers fast and effective product support.

It’s difficult to isolate and modify specific rules that cause false positives.

It is effective against known vulnerabilities.

Amazon Web Services (AWS) WAF

The Amazon Web Services WAF is a cloud-based and on-premises web application software that monitors and protects your web application from malicious web traffic and attacks. The AWS web application firewall is made mainly for Amazon web services users, so it's easily integrated with Amazon CloudFront Distribution, Amazon API Gateway, REST API, Application Load Balancer, Cognito User Pool, etc.

With AWS WAF, you can access additional minutiae details that help create stronger firewall protection against cryptic attacks. Some of these details include the country of origin of a request, string match or regular expression, the presence of XSS or SQL codes in a URL, etc.

Features of Amazon Web Services (AWS) WAF

  • Full-feature API

You can control the AWS WAF via APIs, which makes it easier to create and include the WAF’s rules during your app’s design and development process. This feature also smoothens communication and process transmission between the app development and security team.

  • Real-time Visibility

Because the AWS WAF is integrated with Amazon CloudWatch, it provides real-time details of requests accessing your web app. It also quickly alerts you when a rule’s threshold is exceeded and provides the details of the defaulting request.

  • Bot Control

The AWS WAF has a managed rule group named AWS Bot Control. This rule group can be used with custom or managed rules, giving you details on the activity of all the bots (both common and pervasive bots) trying to access your web app.

Pros and Cons of Amazon Web Services WAF



It is easy to deploy.

No pre-emptive zero-day protection due to use of signatures

It is effective against pervasive bot attacks.

Requires constant tuning of signatures to avoid false positives

It is easily integrated with other AWS products.

Logs are not very detailed.

It uses free and paid rules to customize web app security.

It doesn’t increase web latency.

open-appsec WAF review

Are you looking for a way to block attacks on your web application before they happen? open-appsec uses machine learning to continuously detect and preemptively block threats before they can do any damage. Our code has also been published on GitHub, and the effectiveness of our WAF has been successfully proven in numerous tests by third parties. Try open-appsec in the Playground today.

The open-appsec WAF protects your web app by using machine learning to monitor the traffic trying to access your app. This advanced web application security method differs from traditional WAFs because it doesn’t use rules, signatures or policies to filter out malicious traffic.

While the use of signatures has successfully protected web apps from known vulnerabilities, it doesn’t have a good history of protecting apps from unknown vulnerabilities and zero days. And so the open-appsec WAF uses a machine-learning-based firewall to find trends that give insight on how to protect your web app against zero days, SQL injections, XSS, OWASP top 10 attacks and other web attacks.

Also, the open-appsec WAF is an open-source web application firewall and has been independently verified by third parties like Claroty Team82. It can be used as an add-on for various tools like Terraform, GraphQL, etc., and uses declarative configuration to help you save time while declaring the exact steps for a system process/outcome. Try open-appsec in the Playground today.

Features of open-appsec WAF


A WAF's primary duty is to protect web applications from attacks like SQLi, XSS, session hijacking and other web attacks, so most popular WAFs don’t have a functionality dedicated to preventing pervasive bot attacks. Some with a bot prevention functionality create rules using known characteristics that don’t protect web apps from the ever-adaptive and evasive bots created daily.

Because of these reasons, the developers of the open-appsec created a WAF that uses machine learning to pool details from protected endpoints across the globe to continuously update its algorithm in real time. This, in turn, helps it to detect both new and old bots and protect your app. No rules, patches or maintenance is required.

Request Monitoring Using ML

The open-appsec WAF doesn’t use rules, signatures or policies; instead, it uses machine learning to discover how people use your apps. Insights from this process help it differentiate a malicious request from a legitimate request. It then further investigates the malicious request and stores data from it in its offline ML model for future reference.

This open-appsec feature eliminates the need to carry out software updates, maintenance or patches and reduces the chances of false positives.

API Security

API calls make up more than half of the web traffic, from open to partner API calls. While these API calls automate communication and efficiency in web applications, malicious API calls can inject malware into web apps or trigger DDos attacks.

To prevent this, open-appsec WAF helps monitor and keeps track of all your API endpoints and hardens your API attack surface to keep your API activity within safe limits. It uses machine learning to provide real-time data to help you understand the efficiency of your API and blocks malicious API calls using OpenAPI schema.

Try open-appsec in the Playground today.

Pros and Cons of open-appsec WAF



It has a free version.

It has a small community.

It provides a proactive defense against web attacks.

It is a fairly new WAF.

It is an open-source firewall.

Due to the lack of threat signatures, rules and exception handling, it simplifies system maintenance.

It declares actions and results using a declarative system configuration.


In conclusion, the WAFs mentioned above have their strengths and weaknesses, making each suitable for different use cases.

ModSecurity WAF is highly customizable and an open-source solution; AWS WAF offers advanced security features and integrates with other AWS services, while open-appsec provides a pre-emptive WAF solution by using machine learning to protect your web app from web attacks. Try open-appsec in the Playground today.

So, when choosing a WAF solution, it is important to consider your organization's security needs, deployment preferences and budget to help you make an informed decision and ensure the security of your web applications.


Is NGINX ModSecurity WAF free?

While the ModSecurity WAF is open-source and free, its NGINX module is not free. The NGINX module provides access to updates, bug fixes, and technical support and so it requires a paid subscription.

What is a WAF, and what are the different types?

A Web Application Firewall (WAF) is a security solution that protects web applications from various types of web attacks by monitoring incoming traffic and filtering out malicious requests.

There are two main types of WAFs:

  1. Network-based WAF: installed at the network level and acts as a proxy between the internet and the web application.

  2. Application-based WAF: integrated directly into the web application. It provides a more comprehensive security solution because it can access the application's code and logic.

How does ModSecurity work

ModSecurity works by operating as a reverse proxy and sitting between the client and the web server. It intercepts incoming requests, analyzes them, and applies the ModSecurity core rules to determine whether they are malicious or not.


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

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