隐藏ajax调用

In my view point, i think, hiding ajax call from Google Chrome's console or firebug is impossible. However, I'm still curious how these guys on codefights do it. You may check their leader board. Navigating to page 2, page 3... It really looks like AJAX calls but i cannot capture that call in firebug. There isn't any XHR call or js that contains the leader board data... I don't know how they send data to my browser. Does anyone know how they can do it? Is it an AJAX call or not? I really want to apply it to my current project but don't know where to start.

They use websockets. Nothing is hidden.