This handler Telerik.Web.UI.WebResource.axd
serves all resources scripts, styles, images for all Telerik controls including the Captcha. That's why it must be accessible if you plan to have a page with telerik controls for anonymous users.
Handler with query string parameter ?type=rau
is the upload handler. What are your concerns? Are you worried that someone can make a post request to this handler and upload a file wrongfully
into the Temp Folder?
You may try to configure the AsyncUpload to use a Custom Handler
and forbid it for authenticated users.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.