Tech support calls, its pretty blackhat/shady and kinda public knowledge at this point. People are making millions as we speak.
You ever go to a website and get a popup saying your browser has crashed bla bla bla call tech support? That's it.
People pay $5-$10 per call you generate. The person you sell the calls to tries to get the caller to buy some anti virus or something that cost like $400 a year.
The law is cracking down on it so its kinda on its last limbs but it's still going strong if you know the right people.