Poland's support for the Anti-Counterfeiting Trade Agreement, or ACTA, has sparked days of Internet protests by groups who fear it could lead to online censorship.

The sites that are protesting are primarily ones that are popular with young people and carry a mix of celebrity news, jokes, funny photographs and other entertaining material.

One site -- http://www.wykop.pl -- said that "under the banner of fighting piracy and concerns about intellectual property, ACTA will limit the rights of each of us."

However, an influential group representing authors and composers -- known by its Polish acronym, ZAIKS -- has thrown its support behind ACTA. ZAIKS argued that ACTA will not hurt Internet freedom but protect the rights of creators. It said that Internet piracy is now robbing artists and the state treasury of hundreds of millions of zlotys (many millions of dollars) in income.

ACTA shares some similarities with the hotly debated Stop Online Piracy Act in the U.S., which was shelved by lawmakers last week after Wikipedia and Google blacked out or partially obscured their Web sites for a day in protest.

In recent days, a group calling itself "Anonymous" attacked Polish government Web sites, leaving several paralyzed on Sunday and Monday. On Tuesday, most appeared to be working again, though the prime minister's site was unreachable. Still, Polish leaders are vowing to stick to plans to sign ACTA in Tokyo on Thursday.

ACTA has been negotiated by a number of industrialized countries that have been struggling for ways to fight counterfeiting and intellectual property theft -- crimes that cause huge losses to the movie and music industries and many other sectors.

The far-reaching agreement would cover everything from counterfeit pharmaceuticals to fake...