They only find out when the same ip do it but I change mines after every click
Do you think Google Adsense work that way?
Google could find from geographic stats, impression and something else.
Let just say you click, change ip, click again, change ip again. it would make the CTR = 100% and thats enough to get that site banned from adsense
Also geographic stats, 290 clicks from same region, isn't that suspicious?
Then if you using proxy.. no, just don't