Google is taking anti-piracy efforts more seriously by trying to block web sites that convert Youtube music videos to mp3 files. The company also threatens these web sites with legal actions.

According to a report on the TorrentFreak blog, Google has been sending cease-and-desist letters to sites that serve their visitors by 'ripping' MP3s from YouTube videos. The letters threaten legal action if a site doesn't comply. Web sites that have already received such letters include YouTube-MP3.org and Music-Clips.net, according to the report.

YouTube-MP3.org already claims their servers are now being blocked by YouTube so the conversion service has stopped working.