You can limit access to your content to IP ranges.
In CDN Resource settings choose Show Advanced Settings, in the Access (Security) click Add Policy and find IP Access Policy.
By default, there are no restrictions by IP to your CDN Resource. You can set up Allow or Block policy.
Access to the resource is allowed for all of the IPs except for the specified in the field.
Access to the resource is denied for all of the IPs except for the specified in the field.
You can specify IPs only one by one via Control Panel. To add the list of the IPs use API.