Google penguin update was released by Google to combat the web pages with duplicate links and irrelevant content.
This update was released on April 24, 2012 and it is applied to web pages in all languages such as polish, English, German and Chinese etc.
In this update Google will use 3.1% of queries and it may be high in the languages that use more web Spam content. To be protective from the effect of penguin update, check your traffic and make sure it hasn't fallen before 24th April, eliminate all the Spam content, check the links by positioning exact keywords, remove excessive keywords on specific web pages and delete all low quality links that you have received.
Google penguin update attacks the web sites with keyword stuffing, hidden content, link farms and plagiarized content.