The nonprofit organization that sponsored the report, Peacefire.org, is itself being blocked by a group of Internet service providers.

The study suggests that news and information sites like that of Amnesty International are often blocked by Internet filters that search for words like "death" (as in death penalty), "kill" (soldiers allegedly killed civilians) and "sex" (officials investigate sex crimes). Peacefire says this proves Internet filtering companies do not visually examine suspect Web sites before "blacklisting" them, as is often claimed.

For instance, the report describes one news page on the main Amnesty.org site that is blocked by Cybersitter as "sexually explicit." Peacefire analysis shows that the filtering software blocked such articles because they contained the phrase "at least 21."

The sentence that triggered the filter's block of the site? "Reports of shootings in Irian Jaya bring to at least 21 the number of people in Indonesia and East Timor killed or wounded."

In another example, the entire Amnesty International site in Israel was blocked by Cyber Patrol, according to the study.

The Peacefire report cites dozens of other Amnesty International-related sites that were blocked by Internet filters.

These include the sites of Amnesty International at New York University; Algeria Watch, which includes an Amnesty International report; and Suzanne Vega, an American singer who contributes money to the London-based human rights group.

Peacefire decided to test several blocking programs using a list of Amnesty International sites because numerous students complained that filters kept them from completing school projects.

Brian Milburn, president of Solid Oak Software, the maker of Cybersitter, said, "There's always going to be instances where sites are going to be excluded accidentally." He said a human being reviews individual sites if people report them to the company.

Several politicians in the United States and in other countries have pressed for requirements that libraries and schools use filtering software. These requirements are usually supported by the makers of the software, some of whom have given congressional testimony that all blocked sites are first reviewed by a human being.

Peacefire, however, says filtering programs often block more news sites than sexually oriented sites. In a study released last October, the group tested five blocking programs. Peacefire found that different programs had "error rates" ranging from 20 percent to 80 percent, blocking sites that were not seen as offensive.

Ironically, many Internet users cannot find Peacefire in their Web browsers. That is because the site is the mistaken target of a "black hole" list, according to Peacefire's Webmaster, Bennett Haselton.

The Realtime Blackhole List (RBL) recently placed a block on hundreds of sites at the Web hosting service used by Peacefire.

The RBL is blocking all of these sites because one site sells email automation software that has legitimate uses but could also be used to send "spam," or unsolicited email. To put more pressure on such a site, the RBL simultaneously blocks hundreds of unrelated, innocent sites that, by coincidence, have the same Web host as the site that the RBL dislikes.

The RBL has been criticized by legal experts and sued numerous times. But many Internet communications carriers--including AboveNet, Connectnet and Internet Texoma--still use it to restrict Internet users' access to any sites placed on the list.

Paul Vixie, founder of the RBL and senior vice president of AboveNet's parent company, declined to comment.

Haselton hopes other sites will spread the word that Peacefire has not disappeared. If the block is removed, people whose Internet service happens to pass through carriers that use the RBL may someday have a chance to see Peacefire's report on the dangers of filtering.

Consumer advocate Brian Livingston appears at CNET News.com every Friday. Do you know of a problem affecting consumers? Send info to tips@BrianLivingston.com. He'll send you a book of high-tech secrets free if you're the first to submit a tip he prints.

 
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Brian Livingston has published 10 books, including "Windows 2000 Secrets" and "Windows Me Secrets." He has been a contributing editor at PC World, Windows Magazine, InfoWorld and other magazines for more than 10 years. Before his work as an author, Livingston was a management consultant advising financial institutions on computer technologies. In 1991, he received the Award for Technical Excellence from the National Microcomputer Managers Association for his efforts to develop standards in the computer industry.