Tecadmin published a tutorial about installing mod_cloudflare in Apache on Debian.
How To Install Apache mod_cloudflare on Debian
Cloudflare is the most popular content delivery network service provider. Which also incudes DNS, DDoS protection and security for the websites. In action cloudflare act as reverse proxy server. Once the website traffic is routed with cloudflare network, the backend server don’t know the actual visitor ip.
How To Install Apache mod_cloudflare on Debian