title: How can I implement domain-level security
body: <p>On specific domains, I want to protect embedded links so that they will only work if they are executed in that domain, but if anyone copies the link and uses it somewhere else, it will not work.</p>
  <p>so for example, assume I have the link <a href="http://www.securedLink.com/somefile" rel="nofollow noreferrer">www.securedLink.com/somefile</a>, and a domain <a href="http://www.myDomain.com" rel="nofollow noreferrer">www.myDomain.com</a>, then I want to return 403 if the request didn't come from <a href="http://www.myDomain.com" rel="nofollow noreferrer">www.myDomain.com</a>.</p>
  <p>Initially, I implemented that using the referrer field.
  I check the referer field on the server-side, and if it isn't myDomain, I return 404.</p>
  <p>However, it is very easy to manually add this header...</p>
  <p>Vimeo has a feature called 'domain-level privacy' that accomplishes exactly that.
  I tested it and it appears they are using more than just the referer field.</p>
  <p>What can I do to implement domain-level privacy?</p>