I see that 95% of spam I am getting from Germany, China, Brazil and Russia. In Germany I was able to locate infested part of their telecom network. Russia is different story, Brazil too. I honestly have enough of this junk and I am blocking the whole China, Russia, Brazil and particular network in Germany. Customers will be white listed on request and that is it. To add to the whole lot I am regularly attacked by Chinese hackers and recently it goes beyond point of acceptance. So I have decided to cut of all of those countries one by one on the routers and firewalls and forget about majority of my problems. I suggest to follow the steps. There is no other way to fix it, geolocation based blocking is the way to go and then unblocking legitimate hosts only. When China gets isolated then they will fix their networks. I think it is just a matter of time.