A little over a year after its introduction, the Penguin algorithm was given a major update. As many have discovered, Penguin has had sweeping effects on the way Google deals with sites it considers to be trying to game the system with over-optimization.
Since Penguin first hit the servers, there have been two significant updates. However, both were largely tweaks or minor data refreshes. Penguin 4 introduces a major update to the core algorithm and delves much deeper into sites to detect spammy tactics.
If version numbers confuse you, remember this: Google revised the Penguin spam program three times. They labeled this update Penguin 4. However, they call it Penguin 2.0 because it’s the first major algorithm revision.
Some old SEO “best practices” now hurt a site’s ranking. If site owners gambled and used these tactics, they might have felt relieved when Google didn’t notice at first. But that relief didn’t last. In recent weeks, Google has indeed cracked down on these practices. Consequently, it has effectively collected what was owed in terms of ranking penalties. As a result, many of those websites have likely suffered a significant drop in their search engine positions.

Spammy Backlink Profile
If, in the past, you’ve engaged in questionable link-building practices and accumulated numerous low-value incoming links from spammy websites, then it might be a prudent decision to sever those connections.
Over-Optimized Anchor Text
Naturally, incoming links have varied anchor text. If 90% of your links use the same keywords, Google will likely think they aren’t natural. They might assume you didn’t earn them over time due to your content’s value.
A natural anchor text profile will contain lots of brand name anchor text, unrelated text, and some keywords.
Paid For Links
Buying and selling links that pass PageRank is a top tactic. This tactic will demote a site in the SERPs.
Keyword Stuffing
If you’re still doing this, 2005 would like its SEO tactics back.
Cloaking
Google penalizes sites that use techniques like cloaking or sneaky redirects to show different content to Googlebot than visitors.
Related
Google Penguin Update and Its Impact on SEO – This article from BrightEdge explains the goals and effects of the Penguin update, emphasizing the importance of high-quality content and ethical SEO practices
Anchor Text Optimization: Avoiding Over-Optimization – A Moz resource that provides insights into balancing anchor text to prevent penalties from updates likw

Has your site taken a hit in the last few weeks? Or perhaps you’ve been using the techniques we’ve mentioned and seen no harm to your ranking at all. Feel free to discuss it in the comments below.