External website can use < IMG /> tag to display an image from your site somewhere else on the internet, and The result of this is that the other website steals your bandwidth.
< IMG />
1. Log into your cPanel account.
2. In the Security section, click on the HotLink Protection Icon.
3. If it displays Hotlink protection is currently disabled, click on the Enable button.
How to Configure Hotlink Protection?
Under URLs to allow access: you can allow an external website or your own website to have access. For example, if you have a subdomain like demo.example.com, you can add this website’s URL to the list of allowed websites.