Pornography has been actively traded through file-sharing services from their start.

The Web sites typically charge fees for access while the file-sharing services are free.

The industry blames file-sharing services for a sharp decline in sales in the past three years.

One of the most famous file-sharing services, Napster, became hugely popular in the late '90s.

But he added: "If it's on the person's computer and they're using some type of file-sharing service, there's nothing we can do.

No copies are currently available for purchase but the tracks can be found on many file-sharing services.

In particular, they took advantage of increased bandwidth and hard disk capacity to provide a file-sharing service.

Kazaa was a leading file-sharing service until legal issues shut it down.

The free file-sharing services do not pay royalties.

Back then Napster, the hugely popular file-sharing service had just been shut down by the courts.