I remember hearing on a podcast several years ago that there is this underground network of buying traffic where legitimate websites can someone buy traffic thr

I remember hearing on a podcast several years ago that there is this underground network of buying traffic where legitimate websites can someone buy traffic through these click farm sites (e.g. top 10 X where you have to click next every time). And they can somehow transfer it to their metrics. The basic underlying idea was that pretty much all online advertising and media companies are sitting on fraudulent stats and all advertisers would probably wake up and the bubble will pop. I can't find any information about this in particular because I don't know the term to search for. Does anyone if this is true or how to find out more about this underground network?