The music industry has a new problem and its name is Aimster.

The recording industry is taking on Napster in court but other file swapping systems are quickly gathering fans and may be much more difficult to shut down.

One of the latest, called Aimster, is aimed at users of a software program that is already hugely popular.

It hopes to avoid a legal challenge by restricting the number of people with whom users can swap files.

The legal battle between the Recording Industry Association of America (RIAA) and file-swapping service Napster is due to resume on 2 October.

The RIAA sued Napster claiming the service allows people to breach copyright and swap pirated MP3 music files.

Now Aimster is looking to give users of AOL's instant messaging software the chance to swap files.

The software is used by millions of people to instantaneously send messages to groups of friends who are all online at the same time.

Aimster is an add-on to the software that lets users swap files with the people in their buddy lists. A buddy list is a list of the people to whom a user regularly sends messages.

The Aimster software lets users search for and swap MP3 files instead of text messages. Swapping is done in private forms rather than via a public, central database that Napster uses.

Safe swapping

Files are swapped using the Gnutella service that, unlike Napster, does not have a central database.

Aimster has a readymade audience because AOL claims that it has tens of millions of users of its instant messaging software.

One of the first instant messaging programs was ICQ (I-seek-you) which now claims to have 65 million users. AOL bought ICQ in June 1998.

Aimster hopes to avoid legal action because it only lets friends share files with each other. The US Audio Home Recording Act allows consumers to make copies of copyrighted music to share with friends.

Aimster is already proving popular. Less than a month after it officially launched, the company claims to have about one million users.

Early versions of the software did not work well across firewalls and could only support a limited number of users. Aimster said it would address these problems in future releases of the software.

It remains to be seen whether Aimster avoids the legal action that has been launched against other file sharing services such as Napster and Scour.

Aimster may even attract legal action from AOL. In the past, it has stopped other companies making their instant messaging systems compatible with AOL's.