bad traffic

Hi Everyone, I am curious as to how search engines like Google, Yahoo and Bing and filter out bad traffic, like for example the same person clicking on the same ad multiple times, or someone using a bot to click on certain ads. Also, is there a way "around" this, in a way? For example changing...

My site ussualy recives about 100-200 traffic but from yesterday to recent day my site recived over 2000 traffic. My keyword immediately down rank too, Is that effect to SERPs? Please help, thanks very much

Hey bhw! I would like to ask you a question (please don't bash me.) I launched my website today with 100+ registrations within the next 3 hours. After a couple hours (and 4000 pageviews) I noticed that 50% of the traffic came from India and the philippines. We see them as "bad" traffic...