1. Login to WHM as Root.
2. Under the Plugins section, go to ConfigServer Security & Firewall.
3. Under the CSF tab, type the IP address in the Block IP Address text box which you would like to Deny on the server.
4. Click on the Quick Deny icon.
How to Allow an IP Address in CSF :
1. Login to WHM as Root.
2. Under the Plugins section, go to ConfigServer Security & Firewall.
3. Under the CSF tab, type the IP address in the Allow IP Address text box which you would like to Allow on the server.
4. Click on the Quick Allow icon.
How to check the IP Address is Allow or Deny in CSF :
1. Under the CSF - ConfigServer Firewall.
2. Type the IP Address in the Search iptables for IP address text box, and click on the Search for IP icon.
This is how you can block, unblock and check the IP Address is allow or deny in the CSF.