You can suspend a CDN Resource in the control panel.
Go to the CDN Resources section, click on Settings.
In the list of CDN resources, click Settings next to the CDN Resource, that you want to stop.
Next to CDN Resource move the slider to the left to disable a CDN Resource and save changes. Settings will be applied in 30 seconds. Now if someone requests your CDN content they will get 403 code.
To enable a CDN Resource move the slider to the right and click on Save Changes. CDN content becomes available within 1 minute.