The most common misuse of bandwidth is having programs which you or your children may have installed that allow file sharing, and other people accessing your computer, or it may be a virus broadcasting your personal information out to the Internet.
Both of these can be very damaging, and should be corrected to prevent harm to your computer and information. Common examples of programs, which allow this, are Napster, Morpheous, Kazaa, and Hotline. These programs when installed, allow outside users to access files on your computer. If not set up properly, your personal information is at risk of being sent out onto the internet, or even destroyed.