title: Is it standard to check for proxies with getenv and is it effective?
body: <p>Hey quick question, I am wondering</p>
  
  <ol>
  <li>Do big sites use php's <strong>getenv</strong> function to prevent proxy users from registering or signing in?</li>
  <li>Is it effective in deterring hackers from creating a bunch of accounts for abusive purposes if it is used?</li>
  </ol>