Do you know how they detect those? It looks that even pages with 100 links pointing to only one other site, with spammy domains and keyword stuffed texts still help with Google.
If the algorithms don't catch them, they'll eventually attract the attention of a human Google reviewer, at which point they'll be assessed a manual penalty that will show up in the Search Console: https://support.google.com/webmasters/answer/2604824?hl=en
