You can tell clients to check the http referrer for your domain. That would (mostly) stop people from posting now-useless destination URLs online. http referre

You can tell clients to check the http referrer for your domain. That would (mostly) stop people from posting now-useless destination URLs online. http referrers are easily spoofed, of course, but it'll be enough to prevent most people from sharing secret urls on twitter. You could also pivot and allow people to upload files to your own server, but that's a different story.