Kazaa's owners claim the network's 100 million worldwide users download 3bn files each month, said Tony Bannon, representing Australia's six major record labels.
Network users freely exchange songs and movies without paying royalties to copyright owners.
During the first day of the trial yesterday, court judge Murray Wilcox was shown how the system worked by logging onto Kazaa and searching for songs by artists including Australian singer Delta Goodrem and The Sex Pistols. While they were logged on, the site showed that 2.1m users were online swapping 1.17bn files.
The record company lawyers will try to have Kazaa's owners declared liable for copyright breach and loss of earnings in the civil case. If they succeed, a case next year would likely set the damages the owners have to pay.
The 10 defendants include Kazaa's owners, Sharman Networks Ltd., Sharman License Holdings and Sharman's Sydney-based chief executive officer, Nikki Hemming.
Sharman Networks will insist that while it urges users not to commit music piracy, it has no control over what people do with the network's popular "peer-to-peer" software.
But at the start of a three-week trial in Sydney, Mr Bannon dismissed Sharman's defence, saying Kazaa's owners provide software that helps users filter certain files from the network such as those that could contain viruses or pornography but they don't provide software to filter out files containing copyrighted material. In fact, Mr Bannon said, the large volume of traffic in pirated files is key to revenue generation for Kazaa's owners.