NGINX WAF alternatives: App Protect vs. ModSecurity vs. open-appsec
Tags: nginx, devops, cybersecurity, cloudnative
Published: 2022-11-24 21:02:30

Written by: Rubaiat Hossain

Nginx is a popular web server software that can also be used for caching, load balancing, and reverse proxying. Its asynchronous, event-driven architecture makes Nginx a good choice for high-traffic systems, which is the reason a lot of DevOps engineers and web developers choose to use it. However, having a high-performance web server is only helpful when you protect your web app accordingly.

This is where web application firewalls (WAFs) come into play. WAFs sit between your web app and its traffic, and they filter out malicious HTTP requests. A solid WAF solution can prevent various layer 7 attacks, including the [OWASP Top Ten](https://owasp.org/www-project-top-ten/), [bot attacks](https://www.kaspersky.com/resource-center/threats/botnet-attacks), and [zero-day attacks](https://www.checkpoint.com/cyber-hub/threat-prevention/what-is-zero-day-attack/).


![Web Application Firewall](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/5vxhatwkocmzs9dn0j7e.png)


Since Nginx has different use cases, protecting your application depends on how and where you use it. It's recommended that you have a reliable WAF solution since they block most harmful requests in the first place. In this article, you'll compare three tools—[ModSecurity](https://www.modsecurity.org), [F5 Nginx App Protect](https://www.nginx.com/products/nginx-app-protect/), and [open-appsec](https://www.openappsec.io)—based on their active development, advanced security features, and open source commitment to help you figure out which tool is right for you.

## ModSecurity

ModSecurity is an open source WAF that has been developed since 2002. It's proved to be a great success, and developers across the world use it.

### Active Development

Before addressing ModSecurity's active development, it's important to define what the term *active development* means here. In this article, when a tool is reviewed based on its active development, it's in reference to the program having a continuous development effort and a committed community.

Effective July 1, 2024, Trustwave SpiderLabs, the developers behind ModSecurity, [announced the end-of-life (EOL)](https://www.trustwave.com/en-us/resources/security-resources/software-updates/end-of-sale-and-trustwave-support-for-modsecurity-web-application-firewall/) support for this WAF. The open source community should continue the development of ModSecurity, as the code is freely available and many projects use it. However, commercial support will no longer be available after the EOL date.

[ModSecurity v3](https://github.com/SpiderLabs/ModSecurity#what-is-the-difference-between-this-project-and-the-old-modsecurity-v2xx) has also introduced major changes in how ModSecurity works. The entire WAF is not packed together anymore. Instead, the single libmodsecurity engine is paired with a connector module that interfaces the application with the server. Different connectors are available based on the server and are hosted as independent packages. This means that there's a separate [ModSecurity v3 Nginx Connector](https://github.com/SpiderLabs/ModSecurity-nginx/) project.

### Advanced Security Features

Advanced security features of a WAF are the functionalities that set it apart. As a public-facing component of the internet, modern WAFs require solid defense mechanisms to protect from rapidly emerging new threads and malicious activities.

ModSecurity offers many powerful features, such as continuous inspection of HTTP streams, reliable blocking capabilities, and a robust rule engine complemented by a straightforward rule language called SecRule. What sets ModSecurity apart is its flexibility. You can use its features any way you see fit, from real-time application monitoring to full traffic logging, and URL encoding to web app hardening—the scope of creativity is unlimited.

Its solid HTTP blocking capabilities and flexible rule engine allow ModSecurity to patch vulnerabilities without touching the application itself. This practice is known as virtual patching, and it can protect any app using communication channels like HTTP. However, it should be noted that signature-based solution are reactive by nature, meaning that often signatures aren't available until after vulnerabilities have been known for some time and exploits are put into circulation. 

ModSecurity also excels in logging HTTP requests. Since most web servers log a few pieces of information by default, ModSecurity's effective logging capabilities make it a lucrative choice from a security standpoint.

### Open Source

ModSecurity is an open source project, with its codebase open for third-party contributions. It has an [active GitHub community](https://github.com/SpiderLabs/ModSecurity) of open source developers who maintain the project and fix issues. You can easily fork this WAF and tune features yourself. However, with its backing organization announcing ModSecurity's end of support, you can expect little to no active development from the vendor in the future.

## Nginx App Protect

Nginx App Protect is a premium WAF solution that seamlessly integrates with Nginx and provides robust features for DevOps teams. F5 has acquired Nginx and is actively developing its paid offerings. As a result, Nginx App Protect should be viable for those looking to safeguard enterprise systems and data.

### Active Development

You can expect new features and updates to be added [once every few months](​​https://docs.nginx.com/nginx-app-protect/releases/release-notes-3.12/) to Nginx App Protect for handling newer threats, and support is available on demand. Coupled with [Nginx's extensive documentation](https://docs.nginx.com/nginx-app-protect/) and active community, finding support should be effortless for developers.

### Advanced Security Features

Nginx App Protect is a capable WAF solution that can protect modern web applications, APIs, containers, and microservices. Nginx App Protect follows the same role-based access control policy used by ModSecurity. It benefits from the security rules derived from other F5 security solutions and excels at preventing regular layer 7 attacks. Like ModSecurity it is based on signatures and so usually reactive to [zero day attacks](https://www.openappsec.io/post/zero-day-attack-prevention) as signatures aren't available until after vulnerabilities have been known for some time and exploits are put into circulation.

This WAF solution aligns with modern software architecture and continuous integration, continuous deployment (CI/CD) principles. The platform-agnostic nature and declarative policies used by Nginx App Protect allow engineers to focus on innovation rather than worrying about security right from the very beginning.

The [Nginx Controller App Security](https://docs.nginx.com/nginx-controller/app-delivery/security/concepts/what-is-waf/) allows to manage declarative configuration files for App Protect in a centralized manner. It makes managing Nginx App Protect simpler than ModSecurity, which, though immensely flexible, lacks central control.

### Open Source

Nginx App Protect is a closed source solution. To use the WAF product, you'll need to sign up for a premium offering from F5 Nginx that includes NGINX Plus or NGINX Ingress Plus and a licence for App Protect. U.S. List Prices starts at $362 per month for Nginx Plus for Single Instance and Standard Support, plus $620 per month for the App Protect Add-On for Single Instance.

Although the enterprise nature of Nginx App Protect ensures prompt support and in-depth documentation, the absence of an open source model prevents DevOps engineers or developers from auditing the code themselves and diving deeper into the features.


## open-appsec

open-appsec is a modern-day WAF solution that leverages machine learning (ML) to detect and prevent unknown "zero-day" attacks as well as standard known attacks.

### Active Development

open-appsec is under active development, and the code is open source and public. This move allows for regular feature updates and bug fixes by open source developers. The core open-appsec WAF engine is developed in C++ and is available [via GitHub](https://github.com/openappsec/openappsec).

Additional security components are written in C and Go and are readily available. The developers are actively adding new features and adjustments to the ML-based threat engine. In addition, the open source codebase is updated regularly and offers [thorough documentation](https://docs.openappsec.io/), making it a suitable choice for securing modern-day Nginx systems.

### Advanced Security Features

open-appsec offers several advanced security features, of which the flagbearer is its [ML-based threat detection engine](https://www.openappsec.io/tech). The ML-powered core [automatically prevents OWASP Top Ten and zero-day attacks](https://www.openappsec.io/post/open-appsec-protects-pre-emptively-against-apache-text4shell-zero-day-attack-cve-2022-42889) without requiring any tuning or configurations. The intelligent WAF engine continuously analyzes user behavior and transaction profiles to detect and mitigate threats before escalation.

This shift toward proactive threat mitigation from the reactive approaches utilized by standard rule-based WAFs makes open-appsec a worthy WAF solution for the future generation of web apps.

Moreover, open-appsec's seamless integration with modern CI/CD tools allows developers to spend less time securing apps and more time shipping new builds. It's also a breeze to automate. You can use declarative infrastructure as a service (IaaS) or APIs to take care of heavy tasks.

In addition, open-appsec needs little manual administration. It's an install-and-forget solution that preemptively prevents newer threats and reduces the attack surface significantly compared to traditional WAFs like ModSecurity, which require manual rule enforcement to stop the latest threats. Users of paid solutions like Nginx App Protect must also wait for vendor-supplied signaure/rules for newer vulnerabilities.

### Open Source 

open-appsec provides a fully open source solution that can be audited by third parties or extended by individual developers. As previously stated, the project is hosted on GitHub and has undergone rigorous auditing by independent security experts.

The code is easy to read and understand. You can also compile open-appsec with standard compilation tools, and it makes analyzing program behavior simple using traditional code analysis tools.

This WAF solution also meets the [security standards of the [Open Source Security Foundation (OpenSSF)](https://bestpractices.coreinfrastructure.org/en/criteria/0), which indicates the high quality of the source material. The [advanced machine learning model](https://github.com/openappsec/openappsec#machine-learning-models) of this tool is also open source and available for download by anyone.

## Conclusion

Nginx is one of the most widely used software for serving web content, proxying, and load balancing. However, you still need to secure your Nginx-consuming web apps from threat actors and malware. A solid WAF should be your first layer of defense, as they block harmful requests at the application layer.

In this article, you reviewed ModSecurity, Nginx App Protect, and [open-appsec](https://www.openappsec.io) based on their active development, advanced security features, and open source principles.

ModSecurity is a robust solution that offers an advanced rule engine and an open source codebase. But it lacks active development commitments from the vendor. In contrast, Nginx App Protect is actively being developed and offers intelligent features and CI/CD integrations. However, it doesn't offer any open source edition.

[open-appsec](https://www.openappsec.io) is the only WAF in this list that not only is under active development but also offers the solution as open source software. These, coupled with its advanced ML-based threat detection engine, make open-appsec a viable solution for modern web apps.