CKEditor Rehost Image plugin is a simple add-on for uploading images from external web sites to your server and inserting into editing page.
There are many pros for storing all your site images directly on your own site. The most important of them is that your web site needs to be responsive and must let user view an image even when external site is down. Some webhostings may limit bandwidth for your visitors, some web sites owners can block you as a content thief.
But all these problems will be fixed with CKEditor Rehost Image module. Enable it on your site and you will be able to save (rehost) images onto your site. It is nice twice because of simpleness of rehosting process.
PHP and ASP.NET compatible.