Please note the following requirements to anti-DDoS protection:
1. Nginx must be up and running on your server;
2. The server with ISPmanager must have full permissions to iptables and its modules (provided that ISPmanager is installed on a KVM VPS (not OpenVZ).
You can activate anti-DDoS for required WWW-domains in their configuration forms. For more information, please refer to this
article