From the Actrix Online Informer August 2009

by Rob Zorn

A bit about BitTorrent

This next in our series of articles looking at popular web applications and activities covers BitTorrent peer-to-peer file sharing.

"Peer-to-peer file sharing" simply means two or more computers connecting directly to each other and passing files back and forth. On a popular level BitTorrent  is used mainly to download music files, movies and computer games, which is why it upsets production companies so much. But it also has lots of legal uses, and there are plenty of music, movie and game files that can be downloaded legally. Any type of file can be transferred, so some companies use BitTorrent to distribute large files like software updates etc.

BitTorrent  is very popular because it's so easy to use, there's lots of stuff out there to download, and it's pretty fast.

Here's how it works.

First, a user makes a file (or group of files) available to the network. This first user's file is called a seed and it gets registered as being available by a server called a tracker. We won't deal with how to make and register seeds in this article, however.

People wanting the file can search for it on various websites that keep track of what's available on the various tracker servers. All you need to do to begin downloading (or "leeching") the seed is have some BitTorrent software installed on your computer. Click the link to the file on the website, and your download commences. See below for more on BitTorrent software.

Once you connect and begin to leech the seed file you become known as a peer. The tracker connects you to various other computers (other peers) who also have the file and you start downloading bits of it from each of them, which is what makes it all so fast. It's a good system because it means you take a little bit of the file from everybody, rather than put a drain on just one source. Collectively, all the peers connected together sharing the up and download of a file are known as a "swarm".

Once a peer has successfully and completely downloaded the file, the peer then shifts roles and becomes an additional seed, helping the remaining peers to receive the entire file. All this is done automatically by your BitTorrent software.

In the animation to the right, courtesy of Wikipedia, the coloured bars beneath all of the seven clients in the upper region represent individual pieces of the file. After the initial pieces transfer from the seed (large system at the bottom), the pieces are individually transferred from client to client. The original seeder only needs to send out one copy of the file for all the clients to receive a copy.

The thing to remember however, is that using BitTorrent does eat up your bandwidth. A typical hour long movie file, for example, is around 350 megabytes. Once you have downloaded it, you may well find that you have been uploading it to others at the same time, and that is all traffic that will eat into your allocation if you're on broadband. Dialup users can also use BitTorrent, but the file transfer will still only be as fast as their connection allows, no matter how many peers they are connected to.

BitTorrent software

There are lots of free BitTorrent programs (sometimes called clients) available. One that is currently very popular is µTorrent. It's easy to use and quick to install. You can download it at As stated above, you don't need to do much once it's installed other than click on a BitTorrent link. Programs like µTorrent will then automatically kick in and do the rest of the work for you.

Is using BitTorrent safe?

This is the Internet we're talking about, so nothing's necessarily safe. On the other hand, it's not inherently dangerous as long as your computer is up-to-date with the latest operating system updates, and you have a firewall and anti-virus system in place. These days these come standard with Windows.

If your computer's healthy, other peers can't access any of your other files when you are connected to the swarm. One danger is that they could disguise some malicious software, such as a virus as a movie or sound file that will spring to life and do nasty things once you open it. Another common practice is the seeding of fakes. These look like movie files, for example, but when you try to play them you get a message saying the file is encrypted and if you want to be sent the unlocking code you need first to sign up for a special offer at a link provided. Generally the link will take you to an adult site, or possibly even to a site where malicious software is installed. Bottom line is, if you open up a fake, don't follow the link. Just delete the file.

Because of these problems, websites providing BitTorrent links usually allow members to post comments about the file. If you find something you want, look at what comments have been left. If the file has been around for a while and there are some good comments about it, that's a good sign. BitTorrent users who have downloaded fakes will quickly put comments in to warn other peers.

The legal side of things

Using BitTorrent is not illegal, and neither are the tracking servers, technically, because they only hold information about where a file is, not the file itself. Many tracking sites have been shut down over the years due to legal pressure, but many resolutely carry on despite receiving legal threats by the bucket load.

The actual act of downloading copyrighted files may or may not be illegal depending on where you are, but providing them for others to download is definitely illegal just about anywhere. If you download something copyrighted using BitTorrent you are also making it available to others, so it's hard to avoid being a provider. Be warned, music and movie companies are taking this more and more seriously. See, for example, the story in our Cyberspace News Snippets section this month where a woman was fined NZ$3m just for sharing 24 songs!

On the other hand, some artists such as The Libertines have released demos and movies for free over BitTorrent networks, and The Nine Inch Nails frequently release whole albums that way for a fee. So it's not all bad or wrong, and it could be argued this is a smarter approach than taking legal action. File sharing is so popular that it's never going to be stamped out.

You can use Google to find legal BitTorrent downloads that are either free or that you can pay for using your credit card online.

In an interesting development, one of the biggest BitTorrent tracking sites, The Pirate Bay, is moving to a legal model where licensing fees are paid to production companies, and these will somehow be recouped from some users. The details are still a little vague, but you can read more about The Pirate Bay's move in this New Zealand Herald article.

So that's BitTorrent in a nutshell. It's important enough to warrant coverage, but we are certainly not encouraging the downloading or sharing of copyrighted material. Any downloading you do is entirely at your own risk.


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