OK

, here is my answer to your sub-question: Yes, an external attack can be the reason for terminating a google adsense account. It is difficult to get secured from such attacks.
It's up to google to recognise external attacks. If Google AdSense publishers had more information about clicks (IPs, timestamps), then it would be possible to fight against attacks...
But no application except google's servers tracks all clicks, all broswers, etc. etc.