When Google set out to improve the quality of their search results, they focused on two things: Content quality and link quality. Their Panda update took care of the content quality issue, while Penguin was targeted at link quality. The Penguin algorithm is, more or less, a spam hunter. It’s designed to catch websites that are using spam links or purchasing links to game their way to the top of the search results.
Sites that were creating or purchasing manipulative links were penalized by the Penguin update. Links that are caught by Penguin may include:
Penguin was the nail in the coffin for quite a few websites that were already penalized from the Panda update. At the time of the release, there were unethical SEO service providers offering online marketers and businesses alike the promise of quick rankings. These rankings were generated by poor quality links, or links that were purchased on private blog networks or other from other sellers.
As a result of the Penguin update, SEO service providers had to make some major changes to their link building practices. The focus had to shift from link quantity to link quality.
Much like Panda, Penguin also receives updates from time to time. If your website was previously hit by Penguin and you have taken the steps to clean up your link portfolio, you may be able to regain your rankings with a new Penguin update is released.