THEY may not wield battle-axes or wear horned helmets like their Viking forebears, but today’s Swedish pirates are still wreaking some pretty heavy-duty havoc.

The Pirate Bay file-sharing collective, one of the world’s largest facilitators of illegal downloading, is only the most visible member of a burgeoning international anti-copyright — or pro-piracy — movement that is striking terror in the heart of an industry that seems ever less capable of stopping it.

When the Pirate Bay’s Stockholm headquarters were raided last May and their servers seized, the Motion Picture Assn. of America thought it had scored a major victory. “Swedish Authorities Sink Pirate Bay,” trumpeted its news release. (As has since been pointed out, this is a mixed metaphor.) But the rejoicing didn’t last long. The site was back online three days later, and worse yet for Hollywood, the raid and several mass protests afterward generated so much sympathy for the pro-file sharing cause that both candidates for prime minister announced publicly that they did not think young file-sharers should be treated as criminals.

Sweden’s state-registered Pirate Party also benefited from the raid’s fallout. Its membership has now grown to almost 9,000, closing in on the nation’s Green Party (9,550), which holds 19 seats in Parliament.

But the renegades back at the Pirate Bay don’t care for politics. They are, after all, pirates. The group’s website is a database of 500,000 copied movies, TV shows, songs, games and software titles. Instead of pointing you directly to a downloadable song or movie — like Napster used to — the Pirate Bay provides a kind of digital treasure map. The map, called a torrent file, points your computer toward all the little fragments of the booty that are hidden around the Internet. Feed the torrent file to your downloading software, wait a couple of hours, and ta-da! You now have a shiny new copy of “The Bourne Supremacy.”

Also, you have become a criminal.

Well, join the club. The Pirate Bay alone claims more than 5 million active users. According to Internet traffic ranker Alexa.com, it’s the 292nd most popular site in the world. (Netflix is 382; the U.S. Postal Service is 385; Wal-Mart is 391.) Some estimates say that file sharing accounts for 80% of the Internet traffic generated by home users. Last year, the MPAA released the results of a study it had commissioned to gauge the effects of illegal copying. In 2005, the report said, the worldwide motion picture industry lost more than $7 billion as a result of Internet piracy.

This number was widely quoted as evidence of piracy’s economic harm.

Even Los Angeles Mayor Antonio Villaraigosa jumped in. “It’s not just Hollywood that is affected,” he said in December. “It’s not the big stars. It is the people behind the scenes and small mom-and-pop video stores and hometown theaters.”

(The MPAA used remarkably similar language in a statement for this article: “It’s not just Hollywood that feels the impact; piracy hurts Mom and Pop video stores, hometown theatres everyone involved in making and distributing movies.”)

However, critics have been skeptical. As Timothy B. Lee, an adjunct scholar at the Cato Institute, points out, the report was just a summary, not the study itself, meaning neither its results nor its methodology can be independently verified.

Lee is not surprised by the MPAA’s decision to keep the details of the study away from public scrutiny. “What they’re interested in is having a big number for the headlines,” he said.

Could be. But if so, who can blame them? For a decade, the industry has shut down one file-sharing service after another, each bigger, faster and harder to dismantle than the last.

“The technology will always be one step ahead,” said Peter Sunde, the Pirate Bay’s head software designer. The Pirate Bay “is not going to be needed in a couple of years — there will be better systems. Everything is going to evolve. It’s just getting easier and easier to connect.”

Sunde also spoke about the Pirate Bay’s upcoming project to design its own next generation file-sharing technology, one of its goals being to make every transaction completely untraceable. The project will be open source, meaning programmers from all over the world will be able to contribute.

The Pirate Bay has built its reputation on taunting big entertainment and scoffing at copyright law. One of its claims to fame is its online gallery of legal threats, each of which is appended with a less-than-polite riposte from the pirates. One reply to DreamWorks’ legal team read, “It is the opinion of us and our lawyers that you are morons, and that you should go” — etc.

But the Pirate Bay does have a more adult side. Its guiding principle is that the current copyright system is outmoded. “The culture is growing from using file sharing,” Sunde said. “A basic human feeling is the need for new ideas and new concepts. We need to be influenced.”

Nor are the pirates so base as to be against paying artists for their work. In fact, the group’s next venture is a music sharing site called Playble.com, where users will have the option of paying whatever monthly subscription fee they can afford. Every time a user downloads a song, the artist gets a portion of his fee. Sunde says he approached a major record company — he wouldn’t say which — about a partnership. An executive did not take kindly to the offer, and, according to Sunde, accused the Pirate Bay of perpetrating a disturbingly Viking-like act on the executive’s livelihood and family. Hint: He didn’t say “pillage.”

david.sarno@latimes.com