How to prevent user creating certain domains
You can use cPanel & WHM to prevent users creating certain domains. You can do this using the WHM Tweak Settings option labeled Prevent cPanel users from creating specific domains. For cPanel security purpose, this feature is very useful for admins. if you wish to prevent cPanel users from attempting to park a well-known domain (such as google.com, yahoo.com ) onto his or her own domain.
You cpanel customers may be used unknown parked or addon domains to send spam emails or malware functions, so that we have used this options to prevent cPanel user creating certain domains.
You can add to the list of domains to which WHM applies this feature:
To see which domains WHM already blocks, view the file /usr/local/cpanel/etc/commondomains.
Create the file /var/cpanel/commondomains.
In /var/cpanel/commondomains, list the domains you wish to prevent cPanel users from creating.
1) You must separate domains with a newline.
2) You should only list domain names in /usr/local/cpanel/etc/commondomains (e.g. example.com). Listing a domain name will automatically prevent the creation of subdomains for the specified domain. For example, listing example.com will prevent users from creating sub.example.com. In addition, domains listed in this file should not contain a leading dot.
4) Make sure that, on the WHM -> Tweak Settings screen, Prevent cPanel users from creating specific domains is turned On