title: Detect if user is behind a proxy server
body: <p>I know this question has been asked a few times but I just can't find a solution! I own a dating site and have issues with people signing up through proxies (I assume) and spamming my users and creates fake account.</p>
  
  <p>How can I detect if a user is behind proxies like Vtunnel, Hidemyass, TOR etc. I understand there is no guaranteed way but sites like pof.com (plenty of fish) have excellent proxy detection.</p>
  
  <p>I just need to start somewhere.. even if I can just detect the most popular proxy sites.</p>