Penguin is a filter designed to optimize sites that are included in spamming search results and it is a part of the core ranking algorithm.
Designed to prevent web spam, Penguin affects sites that attempt to manipulate the rankings by artificial links. At the same time, sites that do not make use of these techniques benefit from the space given in the search results.
Google automatically searches for a repeated content in the profile links of the sites in its index. When given a positive, it applies an algorithmic penalty which translates into a drop in the rankings. Some of the affected sites become candidates for subsequent manual review.
Although the impact of the update is less than the Panda according to official data, many sites notice their influence due to the common practice of creating links against the guidelines of the search engine.
At the moment is developing new versions to come. In fact, it is expected a future version capable of updating without human intervention.
Penguin 4.0 has launched update on 23 Sep 2016. After nearly two years of waiting, Google finally launches Penguin 4.0. The new Penguin is updated in real time, which means no wait for a new version to see its effects, but recalculates each new tracking signals. Because of this Google says that he will not comment on future updates to the algorithm (as happened with Panda). Another feature is that it works in greater detail, adjusting its effects at the level of spam instead of acting on the entire site. More information about their impact is yet to come.