Yahoo patent Trustrank and was adapted by Google out of a need to test web sites for quality links and to combat spam linking efforts. Due to large numbers of webmasters and site owners going to great lengths to get higher rankings with paid links, link farms and other violation of Google's terms of service ' Webmaster Guidelines ; Google submitted a patent in 2004 regarding the use of TrustRank .
Google has been using human editors to take reasonable chunks of websites to review their links. Web sites that have quality links are given TrustRank status. This status is then used to judge other web sites that are directly linked. It is now becoming more evident that TrustRank is in full effect after the last updates and the rollout of Matt Cutt's BigDaddy update.