Google: Pirate Update
Google’s Pirate Update is a filter introduced in August 2012 designed to prevent sites with many copyright infringement reports, as filed through Google’s DMCA system, from ranking well in Google’s listings. The filter is periodically updated. When this happens, sites previously impacted may escape, if they’ve made the right improvements. The filter may also catch new sites that escaped being caught before, plus it may release “false positives” that were caught.