BrianXShen Usually these numbers are being reported by others on the internet on bad number reporting sites. You can find where numbers are reported by taking one of the numbers reported here and put that number into a Google search. It will show where others have reported that number.
The tech support scam numbers are found in popups. Somewhere on this forum there is discussion on how to find the popups. Basically you enter a misspelled web site. Like for www.youtube.com, misspell it like this www.youtibe.com and sometimes you will get a popup with a tech scammer number.