BitTorrent

BitTorrent is a torrent downloader which is mostly infected by OpenCandy Adware and other PUPs, and while it can be installed without the adware, it is usually installed with the adware.

BitTorrent is avalible with Windows, Mac OSX, and Android.

Several studies on BitTorrent have indicated that a large portion of files available for download via BitTorrent contain malware. In particular, one small sample indicated that 18% of all executable programs available for download contained malware. Another study claims that as much as 14.5% of BitTorrent downloads contain zero-day malware, and that BitTorrent was used as the distribution mechanism for 47% of all zero-day malware they have found.