Google has just released Penguin 2.1--an update to the search engine's spam fighting algorithm. This is the fifth confirmed release of Google’s “Penguin.” The release is a slightly improved version of Google’s “Penguin 2″ second-generation technology.
Penguin periodically looks for sites that are deemed to be spammy but still ranking well, and punishing them. If a website is hit by Penguin, they will see a significant drop in traffic and SEO ranking. Websites can recover from the rank drop by disavowing bad links or manually requesting those bad links to be removed.