clipped from: lifehacker.com 
BitTorrent tracker Vertor verifies, scans, and previews BitTorrent downloads so you don't end up with viruses or bum downloads. It does so by downloading every torrent it finds and scanning the files for viruses. If the download is a video, Vertor takes extracts stills from the video and posts them on the site so you can get a better idea of the content and quality of the download in question.