N2H2 spokesman Allen Goldblatt explained that sites blocked were free home pages, which schools often ask to be blocked as part of its filtering package. Free home pages are sites created by individuals and hosted by companies such as GeoCities.
"A lot of people think filtering is just about pornography, but it goes much deeper than that," Goldblatt said.
The study comes as Congress is debating whether to adopt a public filtering proposal that was hurriedly attached to a large spending bill now up for approval. Proponents say the software is necessary to stop children from viewing inappropriate content, such as pornographic and violent images, at schools or libraries. Opponents argue that filtering often overblocks, shielding useful information such breast cancer or AIDS research.
Computer programmer Jamie McCarthy, who worked in conjunction with the Electronic Privacy Information Center (EPIC), said he picked apart N2H2's blocking software because it is widely used in U.S. public schools. He scanned only for political information sites because he believes "it is the most important speech to be protected" by the First Amendment. He said he used a "typical school setting" for his research.
Among the sites McCarthy said were unnecessarily blocked were the pages of the Traditional Values Coalition and those belonging to a club dedicated to getting Hillary Clinton in the commander in chief spot.
His conclusions were posted on EPIC's Web site Tuesday afternoon.
Ken Collins, director of content management at N2H2, debunked the report, saying schools control which categories to block. In other words, one school may cut off sites that carry images of models in lingerie and bathing suits, and another district may not find such information offensive. N2H2 organizes Web sites in 42 categories including free home pages, lingerie and murder/suicide.
N2H2 was also the subject of an earlier report this week conducted by free speech advocate Ben Haselton of Peacefire.org.
In that report, published Monday, Haselton looked at four companies that offer smut-shielding software and found that most blocked sites have nothing to do with pornography, violence or other materials that may harm children.
He ran the first 1,000 Internet addresses listed in the Network Solutions databank on June 14 through four filters: N2H2's Bess, America Online's Parental Controls, Cyber Patrol and SurfWatch. He also studied an additional 1,000 addresses using N2H2's system.
Cyber Patrol and SurfWatch--which have merged since the research began over the summer--showed the highest rate of error. Haselton said he believes that about 80 percent of the blocked sites were legitimate.
AOL' s Parental Controls, placed on the "mature teen" setting, had the least number of errors, though Haselton noted that more pornographic sites slipped through the filter.
N2H2's Bess shut out no sites from the 1,000 addresses but blocked 26 sites in the second grouping, seven of which Haselton said were legitimate.
Collins said he reviewed the seven Web sites targeted in the report and found that four were improperly blocked. He has since adjusted the company's database to exclude the erroneously placed Web sites.
Haselton looked at a different set of domain names when reviewing N2H2's filters. He believed the company had possibly caught on to the study and "fixed" all the errors in the first batch of 1,000 names.
Collins disputed that claim. "We thank Peacefire.org for its report; our database is much cleaner because of it," Collins said. "But he should have used the same group of Internet addresses for the exercise."
Executives from the other companies could not immediately be reached for comment.