Thefacebook.com, the social networking website which has spread across campuses from Harvard to CalTech, eclipsed half a million users yesterday as the site’s creator prepared to unveil his latest project—a file-sharing program integrated with its predecessor.

The program, named Wirehog, allows digital “friends” to connect to each other’s computers and download files, from documents to music to movies.

A preliminary version of Wirehog was released by invitation-only last week. Mark E. Zuckerberg ’06-’07, thefacebook.com founder and Wirehog co-creator, said an official public release of the program is scheduled for early November once bugs in the current version are rectified.

Unlike popular file-sharing programs such as Kazaa and Morpheus, which allow users to search and download among a worldwide network of computers, Wirehog only facilitates downloading between two acquaintances in a fashion more akin to the file-transfer feature on instant messaging programs.

But Wirehog could garner significant popularity—among college students and others—for its social function and personal approach.

“I think Wirehog will probably spread in the same way that thefacebook did,” Zuckerberg said in a telephone interview from Palo Alto, Calif., where he is spending the semester with the program’s co-creators, Andrew K. McCollum ’06-’07 and Adam D’Angelo, a junior at CalTech.

But if Wirehog takes off like thefacebook.com, which reached the half-million user mark yesterday after less than nine months online, it could attract the attention of anti-piracy groups which have lobbied—and waged legal battles—against programs which facilitate file-sharing.

Chad Tilbury, the director of worldwide Internet enforcement at the Motion Picture Association of America, said a program like Wirehog could run a afoul of copyright laws.

“Certainly, we don’t really want to group something like this with these mass engines of piracy like Kazaa and others,” Tilbury said. But he said no file-sharing program would necessarily be immune from litigation.

“It’s certainly going to be something in the future that we’re going to continue to look at,” Tilbury said.

A spokesman for the Recording Industry Association of America said he was unaware of Wirehog, but he raised concerns that the program could facilitate the transfer of copyrighted music.

“Not only is it illegal, it deprives those who produce the music the ability to benefit from their creative efforts,” said spokesman Jonathan Lamy.

But Zuckerberg said he was not concerned about possible litigation from the movie or recording industries.

“I honestly don’t think it should be a problem,” he said.

Having spent the summer navigating a sea of programming code, Wirehog’s creators said they were confident the program would be able to connect any two computers, even those behind firewalls, which can hinder access and typically prohibit file-transfers on programs like AOL Instant Messenger.

Zuckerberg said they were able to program several “tricks” to get around firewalls and were confident Wirehog would work seamlessly in its official release. He said almost all users of the beta version have had success with the program, though a reporter who attempted to access other Wirehog pages from behind a firewall at The Crimson encountered several problems.

Zuckerberg said advertisements on thefacebook.com would pay for Wirehog. He said Wirehog would likely feature some sort of advertising in the future but will remain ad-free for now.

Advertising revenue will also pay for new servers and power to accommodate increased traffic on thefacebook.com. Zuckerberg said they expected to reach a million users on thefacebook.com by the end of the year.

—Staff writer Zachary M. Seward can be reached at seward@fas.harvard.edu