In a traditional pattern for Apple, copies of the current build of Mac OS X 10.5 Leopard have begun to leak onto the internet.
Right now, a build of the OS is circulating on file-sharing networks, including BitTorrent.
The software - which claims to be a copy of the beta software distributed to developers at last week's WWDC event - began to emerge over the weekend.
Apple offered a ten-point public peek at its new OS at last week's Developer's Conference, and copies of the software were given to attendees at the show so they could begin tweaking their software offerings for the new OS.
The company is likely to take a very dim view at the leaks. A similar incident last year saw Mac OS X 10.4 released without authority online. Apple tracked down and litigated against the developers responsible for the leak.
Developers attending WWDC have signed strict and enforceable legal agreements not to distribute Leopard through file-sharing networks.
Early reports from people claiming to use the software claim that certain parts of it "feel" incomplete. Apple last week told the public that it intended keeping some features secret as Mac OS X heads for its show down with Microsoft's new Vista OS early next year.
Meanwhile, a Windows-focused website last week described some additional features that will debut with the new OS.UPDATE: New reports reveal that this particular download may be a hoax. It appears on BitTorrent search engines as a 4GB disc image. On download, the large file turns out to be devoid of any data, a report claims.