They will typically set up several generic websites with ads, and set their click farm loose to represent fake traffic while clicking on ads for X% of impressio

They will typically set up several generic websites with ads, and set their click farm loose to represent fake traffic while clicking on ads for X% of impressions. You could also be a mercenary and drive traffic to other website operators who want traffic/rev, or even dilute quality/waste spend on competitor ad campaigns. Since these click farms are typically just infected computers, they can likely setup other tasks to monetize: DDoS, email, BTC mining, etc...