Google Penguin is a codename[1] for a Google algorithm update that was first announced on April 24, 2012. The update was aimed at decreasing search engine rankings of websites that violate Google's Webmaster Guidelines[2] by using now declared Grey Hat SEM techniques involved in increasing artificially the ranking of a webpage by manipulating the number of links pointing to the page. Such tactics are commonly described as link schemes.[3] According to Google's John Mueller,[1] as of 2013, Google announced all updates to the Penguin filter to the public.[4]