What do you think they might be looking for that could be detected pretty quickly? I'm wondering if it is something like they can track mouse movement and calculate when a mouse is moving too cleanly, so adding some more human like noise to the mouse movement can better bypass the system. Others have mentioned doing too many actions too fast, but what about potential timing between actions. Even if every click isn't that fast, if they have a very consistent delay that would be another non-human sign.