ModSecurity is described as 'Open source web application firewall. Working embedded in the web server, or standalone as a network appliance, it detects and prevents attacks against web applications' and is an app in the network & admin category. There are eight alternatives to ModSecurity for a variety of platforms, including Linux, Self-Hosted, SaaS, Web-based and VirtualBox apps. The best ModSecurity alternative is BunkerWeb, which is both free and Open Source. Other great apps like ModSecurity are CacheGuard Gateway, BitNinja Server Security, UUSEC WAF and Imunify360.
Because it's open-source, free, ML-based and integrates with NGINX