A new Napster-like program has sprung up online that piggybacks on America Online's popular instant messaging service, limiting swaps of music and other files to close, trusted groups of people.

Launched Tuesday, the Aimster software draws on AOL Instant Messenger's (AIM) buddy lists to create a group of people authorized to swap files with each other. The software then uses Gnutella's open-source technology to make connections between people on the buddy lists. The developers say they are hoping to create a file-sharing system without the uncertainty involved in opening personal computer hard drives to random strangers online. "We're trying to answer the criticisms of file-sharing programs that a number of people have made--that if you're sharing files from your computer, you want it to be personal, not with a million strangers," said John Deep, a spokesman for the group of programmers that created the software. In the process, the developers have selected one of the most popular pieces of software online to target a pool of people. AIM has more than 61 million registered users, according to AOL. But trying to make the software work with AIM has its risks. AOL has consistently blocked other companies from piggybacking on its work, publishing protocols for the software but refusing to allow other message programs to connect with AIM users.