NAXSI is web application firewall.
NAXSI stands for Nginx Anti XSS and SQL Injection.
NAXSI is Nginx module
NAXSI config contains rules.
NAXSI has a very interesting auto-learn feature.
NAXSI filters GET and POST requests.
NAXSI is OpenSource and free for personal use.
NAXSI for Nginx is similar as ModSecurity is for Apache.