Help identifying proxies

I manage Adwords campaigns of some companies and I am trying to find a solution for fraud clicks. I need help with identifying which clicks were generated from proxy servers so that I can put the IP range or the IPs in the exclusions list. I don't know if it is possible at all or if it is possible for public IPs and not for private IPs. I would appreciate ideas on minimizing loss due to fraud clicks or those by your competitors.