A judge in Australia has found Kazaa and associated parties liable for indirect copyright infringement, and has tentatively imposed a partial remedy that requires Kazaa to institute keyword-based filtering.

The liability finding is based on a conclusion that Kazaa improperly “authorized” infringement. This is roughly equivalent to a finding of indirect (i.e. contributory or vicarious) infringement under U.S. law. I’m not an expert in Australian law, so on this point I’ll refer you to Kim Weatherall’s recap.

As a remedy, the Kazaa parties will have to pay the 90% of the copyright owners’ trial expenses, and will have to pay damages for infringement, in an amount to be determined by future proceedings. (According to Kim Weatherall, Australian law does not allow the copyright owners to reap automatic statutory damages as in the U.S. Instead, they must prove actual damages, although the damages are boosted somehow for infringements that are “flagrant”.)

More interestingly, the judge has ordered Kazaa to change the design of their product, by incorporating keyword-based filtering. Kazaa allows users to search for files corresponding to certain artist names and song titles. The required change would disallow search terms containing certain forbidden patterns.

Designing such a filter is much harder than it sounds, because there are so many artist names and song names. These two namespaces are so crowded that a great many common names given to non-infringing recordings are likely to contain forbidden patterns.

The judge’s order uses the example of the band Powderfinger. Presumably the modified version of Kazaa would ban searches with “Powderfinger” as part of the artist name. This is all well and good when the artist name is so distinctive. But what if the artist name is a character string that occurs frequently in names, such as “beck”, “smiths”, or “x”? (All are names of artists with copyrighted recordings.) Surely there will be false positives.

It’s even worse for song names. You would have to ban simple words and phrases, like “Birthday”, “Crazy”, “Morning”, “Sailing”, and “Los Angeles”, to name just a few. (All are titles of copyrighted recordings.)

The judge’s order asks the parties to agree on the details of how a filter will work. If they can’t agree on the details, the judge will decide. Given the enormous number of artist and song names, and the crowded namespace, there are a great many details to decide, balancing over- and under-inclusiveness. It’s hard to see how the parties can agree on all of the details, or how the judge can impose a detailed design. The only hope is to appoint some kind of independent arbiter to make these decisions.

Ultimately, I think the tradeoff between over- and under-inclusiveness will prove too difficult – the filters will either fail to block many infringing files, or will block many non-infringing files, or both.

This is the same kind of filtering that Judge Patel ordered Napster to use, after she found Napster liable for indirect infringement. It didn’t work for Napster. Users just changed the spelling of artist and song names, adopting standard misspellings (e.g., “Metallica” changed to “Metalica” or “MetalIGNOREica” or the Pig Latin “Itallicamay”), or encoding the titles somehow. Napster updated its filters to compansate, but was always one step behind. And Napster’s job was easier, because the filtering was done on Napster’s own computers. Kazaa will have to try to download updates to users’ computers every time it changes its filters.

To the judge’s credit, he acknowledges that filtering will be imprecise and might even fail miserably. So he orders only that Kazaa must use filtering, but not that the filtering must succeed in stopping infringement. As long as Kazaa makes its best effort to make the agreed-upon (or ordered) filtering scheme work, it will have have satisfied the order, even if infringement goes on.

Kim Weatherall calls the judge’s decision “brave”, because it wades into technical design and imposes a remedy that requires an ongoing engagement between the parties, two things that courts normally try to avoid. I’m not optimistic about this remedy – it will impose costs on both sides and won’t do much to stop infringement. But at least the judge didn’t just order Kazaa to stop all infringement, an order with which no general-purpose communication technology could ever hope to comply.

In the end, the redesign may be moot, as the prospect of financial damages may kill Kazaa before the redesign must occur. Kazaa is probably dying anyway, as users switch to newer services. From now on, the purpose of Kazaa, in the words of the classic poster, may be to serve as a warning to others.