Sites like the Pirate Bay and uTorrent haven't enticed hundreds of millions of people to download endless amounts of free media content without making a few enemies. Those BitTorrent giants -- and others like them -- have built their businesses by outwitting the seemingly hapless MPAA and RIAA. The increased acceptance of illegally downloading media has affected the bottom line of the movie and music industry over the past decade, and that isn't good news for torrent fans.

Earlier this month, the BBC reported on a study by computer scientists at Birmingham University designed to find out how risky it is for file-sharers to upload and download files online.  When someone downloads a torrent file from an open site like the Pirate Bay or uTorrent, their IP address is linked with other IP addresses around the world that are hosting that file. The risk is that an IP address is akin to a computer's online fingerprint, an often ignored fact that the MPAA and RIAA haven't hesitated to exploit.

Now, those organizations are planting files online that they think people are the most likely to download. The Birmingham University researchers told the BBC they were "surprised" by the amount of monitoring agencies hired by the MPAA and RIAA do online. The study, which spanned three years, found that IP addresses and other data are being collected for future use.

"You don't have to be a mass downloader. Someone who downloads a single movie will be logged as well," the lead researcher told the BBC. "If the content was in the top 100 [most popular downloads] it was monitored within hours. Someone will notice and it will be recorded."

The copyright police are banking on the idea that there are more people illegally sharing major movies like "The Avengers" than stealing music from small, independent record labels.

It is still unclear how willing courts will be to prosecute individuals based only on the fact that their IP address was recorded. This month a U.S. appellate court ruled that is was not unconstitutional for the RIAA to sue for $222,000, according to Torrent Freak.

The New Scientist reports that "anyone who has downloaded pirated music, video or eBooks using a BitTorrent client has probably had their IP address logged by copyright-enforcement authorities within three hours of doing so."

Since the SOPA/PIPA legislation, which was designed to allocate boost the federal government's copyright enforcement powers, failed to make it through Congress last year, the MPAA and RIAA have gone into a full war footing. They successfully pressured the Department of Justice to halt Megaupload and managed to prod the Ukrainian government into shutting down Demonoid, the popular private tracker.  

The next step seems to be bring Internet service providers like Comcast and Time Warner into the act. Someone breaking copyright laws by regularly downloading movies is using more bandwidth than the next-door neighbor who's just streaming funny videos on YouTube. At that point, third-party monitors might take a closer look into what someone is doing online.

Lifehacker reports that perhaps the most common way for ISPs to fight BitTorrenting is to "throttle" a user's Internet connection, slowing it down or even cutting the connection off. The practice is most prevalent in Canada, where it's had little effect. ISPs are also known to have fielded requests from copyright enforcers who pressure them to give up an Internet user's contact information, most often to send the offender a warning letter or a subpoena.

BitTorrent users can avoid throttling or legal trouble by hooking up to virtual private networks and proxies for their connection online. In the latter scenario, someone's IP address is re-routed through another one so a BitTorrenter's real IP stays relatively anonymous to the other users they are connecting with. There are also newer piracy sites that subvert peer-to-peer connections altogether, avoiding the inherent risk of linking to someone who could be working for the MPAA.

Until those methods catch on, the Pirate Bay and other BitTorrent sites will continue their arms race against law enforcement.