You can protect your domain name against unauthorized transfers.
To do so, please log into the management page of the concerned domain name, and use the “Transfer Lock” option in the “General information” section:
Then, just follow the prompts to activate transfer lock.
From your list of domains, select the checkboxes of the domains you want to activate transfer protection on (to select all the domains on the page, click “Page”):
Then, select “Transfer protection” from the drop-down menu in the Batch Changes section below:
Click “Ok” and confirm your choice on the following page:
On the next page, you will see a confirmation message indicating that the operation was either successful or not valid for each domain.