The Sucuri Firewall has several layers of protection, so you don't need to worry about blacklisting IP's.
Our Sucuri Firewall will automatically blacklist the IP address, if it detects continuous attacking requests.
However, if for any reason you want to blacklist an IP addresses from even reaching your website, you can do this by the following:
Click here and enter the IP address you want to blacklist under the Blacklist IP Addresses section.
Click on Blacklist to blacklist the IP address once you have typed it into the box.
With that, this visitor will not be able to even load your website.