Macrovision, one of the largest producers of copy protected CDs, announced this week that the number of copy protected music CDs on the market is now in excess of 100 million.

The company develops the controversial anti-copying technology to produce dual-session CDs which contain both 'red book' audio files that play on traditional CD players and car stereos, and 'second session' data tracks that play on PC CD-Roms.

The technology prevents consumers from 'ripping' audio files to be shared over the internet or copied to another CD.

However, these protected discs have only been released to the markets in Europe, Asia, Australia and Latin America.

The US has not yet been targeted, because reports indicate that American consumers are far less tolerant of the system.

The record companies, on the other hand, love the idea and most major labels are using the technology.

"Record labels are facing unprecedented challenges due to unauthorised file sharing and rampant CD burning," claimed Adam Sexton, vice president of marketing at Macrovision's Music Technology Division.

Bill Krepick, president and chief executive at Macrovision, added: "We have invested heavily in developing our technology over the past several years, and it is gratifying to see our efforts validated by such wide deployment by the major music companies."