Google Penguin
Google Penguin is a search algorithm update, first launched in 2012, that targets sites manipulating rankings through spammy or unnatural backlinks.
Penguin specifically looks at a site's link profile, demoting pages that rely on manipulative tactics like paid links, link networks, and over-optimized exact match anchor text. When it first rolled out it triggered sitewide ranking drops for many sites, and recovery often required cleaning up or disavowing bad links.
Since 2016, Penguin has been part of Google's core algorithm and runs in real time, evaluating links page by page rather than in periodic batches. The modern version tends to devalue spammy links (ignoring them) rather than apply a sitewide demotion, but heavy manipulation can still suppress rankings.
The practical takeaway: build links that look natural to an algorithm scanning for patterns. Diversify your anchor text, avoid buying links in bulk from low-quality referring domain sources, and keep your link velocity believable. Penguin is algorithmic, so it differs from a manual action, which a human reviewer applies.