Following several high-profile court cases, more and more previously illegal file-sharing services are trying to reinvent themselves as legitimate businesses.
However, it is not just the threat of legal action that has caused the change of heart, say some industry watchers.
"They have realised they can make money out of it," said Eddy Leviten of the UK's Federation Against Copyright Theft (Fact).
"They have advertising on their sites and, as those sites attract more eyeballs, they are getting more advertising income."
Popular sites include Isohunt, Mininova and The Pirate Bay. These indexing sites act as search engines for "torrents" files - links to TV, film and music files held on its users' computers.
Peer-to-peer (p2p) software connects users to one another and shares files through means such as so-called bit torrent, which chops up files into manageable bits.
No copyright content is hosted on the websites themselves - they simply do the indexing of the available content.
'Criminal actions'
However, the p2p scene has recently featured in several court rooms.
For example. in 2008 TorrentSpy was told to pay $111m (£67m) in damages for copyright infringement, one of the largest fines ever handed down for copyright theft.

Eddy Leviten, from Fact, on going after the people profiting from stolen content

And recently a Swedish court sentenced four men behind the Pirate Bay site to a year in prison and ordered them to pay 30m Swedish kronor (£2.6m) in damages to entertainment companies such as Columbia Pictures, Warner Brothers, EMI and Sony Music Entertainment.
Following the verdict, the site was purchased for 60m kronor (£5m) by Swedish software firm Global Gaming Factory.
The gaming company is planning to create a legal business model and to pay copyright fees for movies, music and games linked to via the site.
"I think there is a realisation amongst some of these services that they have to go legal and they have to develop ways of working with content owners," said Mr Leviten.
"They are scared that they are going to be targeted by law enforcement, and that's not just Fact, that's law enforcement across the globe as well," he added.
'Free fight'
Another torrent site currently under legal pressure is Isohunt. It was set up by Gary Fung while he was at university and it has become one the most popular indexing sites online.

Popular p2p sites are now starting to change due to the threat of legal action
Organisations such as the Motion Picture Association of America (MPAA) are pressuring it to remove copyright content such as blockbuster movies.
Mr Fung said he has tried to work with copyright owners since the start of the site.
"Anything copyright infringing that they see for distribution online, they ask us and we will take it down, and that is pursuant to copyright laws in the United States.
"The legal challenge is certainly gigantic - we are up against both the MPAA and Hollywood in the States," he admitted.
However, he believes that the law favours copyright owners disproportionately and this makes internet users apathetic.
Isohunt is developing a project called Hexagon which aims to blend bit torrent with social networking and to rationalise the content being shared.
"We are hoping with Hexagon that we can bring in copyright owners in the sense YouTube is doing, in adding advertisements to videos for example, so content owners can use the system to advertise directly off what is being shared," Mr Fung explained.
He believes people file-share because it is a convenient way to access content.
"The question of how do you fight free is by offering something more compelling, more convenient, higher quality and more legal - I think people would embrace it or open up if they do that," said Mr Fung

http://news.bbc.co.uk/1/hi/programme...ne/8212958.stm