Blackhand:
How to properly configure your system for BitTorrent, and use it to
improve your patch downloading experience.
These torrents are extracted directly from Blizzard's downloaders. They transfer data
with all the users downloading the file, either using Blizzard's downloader or using
an extracted .torrent file like this. Check out BitTornado if you need a BitTorrent client. If you're behind a
router, you'll need to forward ports for best performance (which is one reason the
Blizzard downloader usually doesn't work well). http://userpages.umbc.edu/~hamilton/btclientconfig.html has more
info on actually configuring your router/firewall for BT.