Remove DDOS popup while opening my Website

How can i remove this please suggest

If you haven’t made a Firewall rule to perform a security challenge then this message is likely due to your Firewall security setting, the default is “Medium” I believe. You can either change it to something lower or make a Firewall rule to specifically allow traffic from you

Could you please guide me step wise if any idea because i tried much yesterday and removed fireball settings also but that is still coming while opening of the website…