Hackers have broken the security software protecting high-definition movies issued in the new HD-DVD format, the New York Times says.

Copies of the 2005 science-fiction film Serenity were initially made available through a file-sharing system, and now a handful of movies are available, the paper reported Tuesday.

The same day, Edward Felton, a computer science professor at Princeton University who has been monitoring the hackers' attempts to crack HD-DVD on his blog, predicted that they would be successful within days.

The hackers' success could add to the confusion about the competing high-definition formats, HD-DVD and Blu-ray, if high-definition companies choose to upgrade their security features.

But Felton suggested both hackers and companies might want to avoid a confrontation. If the hackers gave the companies a period of monopoly on the movie by not publishing ways of accessing it for a certain time, then the companies might choose to bypass installing better security.

The security software is distributed by InterVideo Inc., a company bought last month by Corel Corp.

The HD-DVD security was partly broken in December, the Times said, when a programmer called  Muslix64 released free software so users could make copies of HD-DVDs in their computers. But they still needed a special "title key" called Advanced Access Content System, produced by the HD-DVD software.

Felton said the title key, used to decrypt the contents of a particular HD disc, can be found on PCs that run the popular WinDVD player. The key is left in the WinDVD memory when it finishes playing a disc, he said.

"This may seem like an elementary mistake, but it is more common and harder to avoid than you might think. Fairly easy methods for capturing these keys are already well known."

He said that websites claim to hold the keys for about 50 HD-DVD movies, a third of the titles available.

"At least some of these title keys are correct. Within days, expect to see a software program that downloads keys from such a site and uses the keys to play or copy discs."

The Times said keys for at least four movies were available Tuesday.

An HD-DVD industry spokesman told the paper the breach was serious, but suggested it was of limited importance and could be remedied.