A San Francisco judge says she may consider pulling the plug on Napster.
District judge Ms Marilyn Hall Patel described the company's efforts to block copyright works from its online music-swapping service as "disgraceful".
But the judge, who is hearing the copyright infringement case against Napster by the recording industry, stopped short of putting her thoughts into action.
She said a court-appointed expert would review claims by the industry Napster was failing to remove copyright material from its service.
Napster's lawyer Mr Robert Silver said "all you need is one file to get through" the song-swapping system's filters, which are designed to remove copyright material and the protected songs will reappear on the site's search index.
Recording Industry Association of America lawyer Mr Carey Ramos said of 5,000 songs the record labels asked to be removed last month 84 per cent were still being downloaded free of charge via Napster.
He commented: "Whatever they're doing, it ain't working."
Ms Patel did not set a new hearing date but ordered technology expert Mr A.J. Nichols to study the issue and see if there was existing technology available to help Napster abide by the court order to remove the songs.
In February a federal appeals court in San Francisco said the judge's order for Napster to remove copyright works shifted too much of a burden on the Internet site.
The appeals panel said the recording industry must first notify Napster of which works should be removed.
PA