In the wake of its legal battle against music-sharing service Napster, the Recording Industry Association of America has upped the ante at the peer-to-peer table.

It's been sending out legal notices to ISPs that it claims are hosting services similar to Napster, said Jonathan Whitehead, an anti-piracy lawyer for the RIAA.

The UK and the rest of Europe's recording industry is waiting to see what happens in the US courts about Napster. Because of the global nature of the internet, the Napster ruling, when it comes, will doubtless affect law and business practice in Europe as well.

Since the beginning of last week the RIAA has sent out 75 legal notices to between 40 and 50 ISPs across the US that host file-swapping servers used in a similar way to Napster.

So far, the RIAA says it's been satisfied with the response from those ISPs. "Every ISP I've spoken to has told me that they would take action concerning these servers, and we've seen a couple of them shut down over the past few days," according to Whitehead.

Making matters complicated for the RIAA is Gnutella, a file-sharing system that doesn't rely on central servers, making it more difficult to shut down. The RIAA would not comment on Gnutella.