Attorneys representing the Eminem's publishing companies, Eight Mile Style and Martin Affiliated, filed a lawsuit in U.S. District Court in Detroit, in an attempt to stop five companies from selling Eminem's songs as cell phone ring tones on the Internet, according to The Associated Press.

The companies named in the lawsuit are Colorado-based Cellus USA, Georgia-based FanMobile, New York-based Nextones.com, New Jersey-based MyPhoneFiles and New Jersey-based MatrixM LLC.

The rapper's representatives are also planning to sue the karaoke companies that sell the rapper's hits for sing-along CDs without owning a proper license.

"This is a big business. We're talking hundreds of thousands of dollars a year," Eminem's lawyer, Howard Hertz, told the Detroit News.

Jupiter Research said in a March report that ring tone revenue is growing nationally, having more than doubled, to $217 million in 2004, and will reach $724 million in 2009.

"We're going to be going after any ring tones or karaoke companies who use his songs without getting the proper licenses," Hertz added.

Eminem, whose real name is Marshall Mathers III, is well-known for his vigilance when it comes to protecting his music.

The famous rapper has previously reached a settlement with Apple, after he sued the company for using a song in an iTunes commercial without asking for his permission.

Eminem also sued The Source magazine, as an attempt to block from publishing the lyrics of unauthorized, racially charged tracks from his early years as a rapper.

The rapper, who has also moved up the release of his last two albums to thwart Internet piracy, is currently in a rehabilitation facility to treat his dependency on sleep medication.