Peer-to-peer (P2P) file-sharing networks such as BitTorrent, eDonkey, and Gnutella provide access to a wealth of computer programs, multimedia, and electronic books, but using them can be risky. Not only do you run the risk of breaking the law by downloading copyright protected material, but you open your computer to adware and viruses. You may inadvertently allow someone else to download your private files.

Know What You Are Getting Into

Research the file-sharing software you are planning to use. Some P2P clients (the software that runs on your computer) come bundled with adware (which displays pop-up ads) or spyware (which tracks your internet usage) or are infected with other malware, such as viruses and key-loggers. Use well-respected software installed from a reputable source.

Read the EULA, Terms of Service and Privacy Statement. They may indicate that by installing and using the P2P software, you are agreeing to more than you bargained for. One very popular P2P program, Kazaa, purposefully comes bundled with malware - a fact clearly disclosed in the Terms and Conditions, should anyone bother to read them.

Understand the copyright risk. Much of the content available on P2P networks is protected by copyright. By downloading copyrighted material, you may find yourself at the receiving end of a lawsuit. Chances are the movie that is still in the theaters you found is a pirated copy.

Install Antivirus and Antispyware Software

Using good antivirus and antispyware software is imperative if you are downloading content from a P2P network. A 2006 study at the University of Indiana showed that 68% of software and "ZIP" files downloaded through the popular P2P client, Limewire, contained malware. The same study showed that queries containing movie titles fetched the most malware.

Before you open or play any downloaded files, scan them with your antivirus software, and delete any in which malware is detected.

Keep Your Operating System Up-To-Date

Many viruses rely on unpatched systems to spread. Configure your computer to update the operating system automatically if possible. Be sure that your antivirus and antispyware software is configured to update automatically as well.

Limit When You Are Connected

Many P2P clients continue to share files after you close the application. Moreover, some P2P clients start up automatically every time you turn on your computer. While this is convenient for sharing files, it is safer to share files only when you intend to. Depending on your client, you may have to go to extra effort in order to turn off your connection.

Limit What You Share

Ensure that you are only sharing files that you intend to share. Check the configuration of the P2P client to see which files it is sharing, and verify that it is not sharing your personal documents.

Use a Separate Account

Consider creating a special account on your computer for file sharing and limiting its rights - specifically removing the right to install software. While it may be inconvenient to log into a different account to share files, the reduced rights of the file sharing account will increase your computer's security.

Beware of What You Download

Attackers try to increase the penetration of their malware by advertizing it as something popular. That first-run movie or popular computer game is likely to contain a nasty virus. Even if it is what it says it is, you may be laying yourself open to a hefty lawsuit if you download it anyway.

No matter what you download, ensure that you scan it for viruses and other malware using respected virus detection software before you open it.

Back Up Your Data

Back up important files that you would want to keep if your computer crashes. Store them on CDs or DVDs and keep them in a safe place. While this is good advice for everyone with a computer, it goes double for those who participate in file sharing, because of the increased risk to your computer.

Discuss File Sharing With Household Members

If anyone else in your household uses your computer, ensure that they understand the risks of P2P file sharing. Keeping your computer free from malware requires cooperation from everyone who uses it.