As much as we advocate holistic SEO here at Yoast, there will always be people turning to the dark side, employing less than savory techniques for their own gain. When someone targets a website with actions intended to lower its ranking in the SERPs, it’s called ‘negative SEO’. One way people can try to damage …Read: "Ask Yoast: Disavow backlinks from shady sites?"
First announced on April 24th, 2012, Google Penguin is a codename for a Google algorithm update aimed at reducing the impact of low quality links to websites. Sites that are deemed to have gamed the search results, by buying or otherwise nefariously acquiring links, can receive penalties when a Penguin update runs that can take away large chunks of their search traffic.
Because Google Penguin doesn’t run continuously (yet), if you’ve been hit by Google Penguin you have to wait for it to run again before your site can be “redeemed”.
Like its sibling Google Panda, Google Penguin has run with intervals of several months up to almost a year, but when it’s run its impact is often huge, causing major changes in the search results.