I can attest that there was at least one such black hat in the 00's. One of my IT guy's mom complained about her machine being slow and having "too many pop up

I can attest that there was at least one such black hat in the 00's. One of my IT guy's mom complained about her machine being slow and having "too many pop ups", so he planned to go to her place on the weekend and fix it. She called back a couple of days later and told him not to bother as it was "all fixed now". o.O I lent him one of our loaner laptops and he brought in her computer back and put it on our test DMZ to see what was up. Yep, somebody had scrubbed all the malware and "search bars" off the machine and installed a free anti-virus package. The exceptions on the anti-virus made it easy to track down what was happening; it was set to send spam every night between 1am and 7am but otherwise was pristine. My colleague had to do some serious soul searching before he decided to wipe it instead of just returning it ...