title: Expire all forms authentication cookies
body: <p>I have a small website with about 10 members. 5 of those are now banned.</p>
  
  <p>I have ensured that they cannot login through the login page.</p>
  
  <p>However because the authentication cookie is persistent and is set to expire after a few months if they return to the site they will still be logged in.</p>
  
  <p>A simple solution is just to expire all authentication tickets/cookies. </p>
  
  <p>How to do that?</p>