Many people like to use MP3 files to copy music so they can listen to it on their computer. Record companies do not like it when people use the Internet to share these MP3 files with each other. They think it is a violation of their copyright. The record industries have a trade group called the RIAA that has taken people to court for sharing music. An Internet website called Napster was shut down because of this. Napster has since re-opened, but does not let people share MP3 files anymore.