Link schemes (also referred to as “link spam”) are attempts to manipulate rankings in Google Search results with unnatural links. Links schemes include links to your website as well as outgoing links from your site.
Google’s Spam Policies for Web Search provide the following examples of link schemes:
Link schemes are an essential part of black-hat SEO, where PBNs and paid links are being used to build link profiles.
Here at Ahrefs, we strongly discourage link schemes. Not only because they violate Google’s guidelines but also because Google can detect a link scheme at any time, and all the efforts and money invested into link schemes will be wasted.
A website participating in link schemes can get a penalty (manual action) from Google.
Besides, Google is constantly fighting link spam and is constantly improving the algorithms that identify unnatural links and prevent them from affecting search quality.