Originally launchd in April 2012, Google Penguin is an algorithm used to fight web spam in the organic search results. The primary function of Penguin was originally to crack down on and penalise, sites using spammy or so called black hat techniques to game their system, like paid for links, or links created automatically en masse with exact match anchor text.
Sites affected by penguin, saw their ability to rank for target keywords drastically reduced and traffic was as a result, severely curtailed. This was in effect a major penalty and was virtually impossible to escape from as Google seldom if ever ran updates. People had to submit a so called ‘disavow’ file, disassociating the affected domain from a text list of linking domains. If the webmaster had included all of the ‘bad’ links, then in the next iteration of the algorithm, the penalty would be removed.
The system was widely decried by the search community as punitive and unfair. Many were of the view that it was easy to attack competitors by way of negative seo; a process of accruing bad links for a competing domain in the hope of negatively impacting their rankings.
Penguin has since been updated (circa September 2016) to so called real time and it has changed from how it originally worked. It no longer directly penalises websites in the sense of bad links will demote your rankings, but will now simply devalue the power of the link to the page, removing its ability to give the page or site the ranking boost expected.
Some have taken the view that it is no longer necessary to disavow bad links as if they are simply devalued then it doesn’t really matter where or how you get your links. However, Google have counselled against this and have reminded users that they reserve the right to manually penalise people caught attempting to game their system.
One would suspect that there are triggers that alert the search quality team to link manipulation transgressions, which are then reviewed for compliance. It’s a good idea therefore, to review your link profile periodically using a tool like Link Risk or SEM Rush and ensure that your disavow file is updated regularly.