Kazaa is one of the most popular of the file-swapping services, which allows users to download peer-to-peer software and use it to access the music, images and movie files stored in other users' computers – all free of charge and mostly in breach of copyright.
Sharman Networks, which is headquartered in Australia but registered in the Pacific island of Vanuatu, has been accused of knowingly allowing the exchange of copyrighted digital material on its network, and cases have been brought against it by recording industries in Australia, the US and the Netherlands.
The Australian action, which began today and is expected to last around three weeks, charges the company, Sharman License Holdings, the firm's CEO Nikki Hemming, Altnet, which bundles software with Kazaa, and others, with copyright infringement.
A ruling is not expected until next year, but precedents abroad have leaned in favour of the peer-to-peer services.
The Dutch action, which came to a head at the end of 2003, resulted in a ruling that the original providers of Kazaa, KaZaA BV, were not acting illegally in making their software publicly available.
The US case against Sharman Networks is still ongoing, but in August the US Ninth Circuit Court of Appeals threw out a similar suit against P2P companies Streamcast Networks Inc., the company behind the Morpheus file-sharing software, and rival Grokster Ltd, on the grounds that, while the companies provide the software used by file-sharers to swap illegally copied digital files, the software can also be used for legitimate purposes.
The US recording industry is hoping to appeal that ruling to the Supreme Court.
Elsewhere, software company Computer Associates International has branded Kazaa's free software as the top internet spyware threat. It gives Kazaa a high "clot factor," its measure of how much a program slows a machine by adding unnecessary registry entries and directories. The higher the clot factor, the more difficult a pest is to remove.
"What we're saying is, it presents a security risk because you're opening your machine and file structures to another 3.5 million peers," Simon Perry, vice president of security strategy for CA told internet news site eWeek.
Kazaa claims its software has been downloaded over 378 million times.