Steps to follow to block IP address through IIS

1. Go to the IIS Manager from Start → Administrative Tools → Internet Information Services Manager
2. In the Connection Panel, expand the server name, expand Sites and then your website.
3. In the Home pane, double-click the IP Address and Domain Restriction Feature.
   
   

4. In the IP address and Domain restrictions feature, click Add Deny Entry in the Actions pane.
5. Enter the IP address that you wish to deny and then click OK