The update is aimed at decreasing search engine rankings of websites that violate Google's Webmaster Guidelines by using now declared black-hat SEO techniques involved in increasing artificially the ranking of a webpage by manipulating the number of links pointing to the page.

It is an google update

The Google Penguin algorithm, first unleashed in April 2012, is a webspam algorithm designed to target websites that use low-quality link schemes to rank high in Google SERPs.