Welcome to the Q&A Forum

I've got clients who are seeing penalties appear recently with backlink profiles like this, where the same content is published on a ton of subdomains of really weak sites. Those backlinks will be seen as spam, guaranteed--the only question is, how long will it be before it hurts your site via either an algorithmic or manual penalty? Any time people are creating a strategy like this, and selling links on all those subdomains to lots of people, it's only going to be a matter of time before it gets on Google's radar.  It might be that some other website gets tagged with a manual penalty, so a Google spam engineer looks at their profile and sees a pile of links from these same subdomains, and says "whoa, Nelly, better add this to our list of Really Bad Places"...and then a month or so later, everyone who has a pile of links from these subdomains gets an algorithmic penalty.  Or, it might happen that 100 other webmasters all disavow links from all of these subdomains, and maybe 100 is the magic # of disavowals that Google uses to determine domains that are most likely spamming. Either way, I'd say the clock is ticking on these subdomains, and if it were me, I'd disavow now, even before the penalty happens.  Remember, you'll need to wait a few months after the disavow is uploaded for it to have an effect anyway....so ideally, you want your disavow to be read just before you get penalized.