ModSecurity for Nginx is a web server module for nginx, because of nginx extensibility model (does not use dynamically loaded modules), I can't just build mod_security like the one for Apache HTTPd, nginx module must be added at compile time.
So I made a repo of a modified Nginx with mod_security support, currently only available for Fedora 20 and EPEL 6 (RHEL 6 / CentOS 6) (can extend it latter - just ask).
I'll try to track the main package version, if you have issues with this repo, email me at athmane (AT) fedora domain or ping me on IRC (athmane)
Next blog post we'll see how to use Core rules set with Nginx
Edit 2: I forgot to specify that ModSecurity for Nginx is a BETA quality and you should not use it in production (for instance large POST requests to backend may timeout).