You can find this section in HostBill Admin → Settings → Security Settings → Banned IPs
This page allows you to ban certain abusive IP addresses from accessing your admin/client areas. The ban can be sat permanently and temporary (by setting a precise date when the ban expires). Note: Every IP you enter in IP Ban form has to match exactly the user IP you want to ban, those bans apply both for HostBill adminarea and clientarea restricting login or registration.
To add IP address to banned IP list simply enter IP address, optionally add the ban reason and choose if/when the ban should expire.