1. Log into your cPanel account.
2. In the "Security" section, click on "IP Address Deny Manager" Icon.
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3. Under "Add an IP address to deny" you should enter the IP Address you wish to block.
4. Click on the "Add" button.
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Here is Example:
Single IP Address: 192.168.0.1
Range: 192.168.0.1-192.168.0.40
Implied Range: 192.168.0.1-40
CIDR Format: 192.168.0.1/32
Implies 10.*.*.* -- 192.