ANN ARBOR, Mich. — A comprehensive new study of Internet filtering software finds that libraries, schools and parents can bar access to pornographic Internet sites without blocking access to important health information. But the findings — based on a study of six filtering packages by University of Michigan researchers — found that effectiveness of the software depends largely on its configuration.
“In general, we found that filters were remarkably good at distinguishing between health information and pornography when set at the least restrictive setting,” said lead author Caroline Richardson, M.D., a lecturer in the university’s Department of Family Medicine. “But at highly restrictive settings, almost a quarter of health sites were blocked — though there was little improvement in porn-blocking over the least restrictive settings.”
Researchers tested which health and pornography sites the different filters blocked — or allowed — depending on how software controls were set. The study compared the filters’ performance in Internet searches based on 24 health search terms and by allowing access to 586 preselected “recommended” health sites for teens. Researchers used a specially designed Java computer program that conducted Internet searches and stored the results in a database.
The team started with unfiltered searches for 24 health and sexuality terms, and six pornographic terms, using six search engines popular with teens — Yahoo, Google, America Online, MSN, Ask Jeeves and AltaVista.
Some of the health terms were unrelated to sex (diabetes); others involved sexual body parts (breast cancer). Some were related to sex (birth control) and some to controversial health topics (abortion).
Researchers then tested whether access to the sites was permitted by several software packages: N2H2, CyberPatrol, Symantec Web Security, SmartFilter, 8e6 and Websense. All are widely used by schools, libraries or both. More than 3,000 health and 500 pornography sites were used to test the filters.
At the least restrictive setting, designed to filter out only pornographic pages, the filter software blocked an average of 1.4 percent of health information sites and about 87 percent of porn sites.
At moderate settings, designed to filter pornography and a few other categories such as nudity and information on drugs and weapons, the filters blocked an average of 5 percent of health sites and 90 percent of porn sites.
At the most restrictive settings, which barred a broad range of categories, the blocking of health sites reached an average of 24 percent, but porn-blocking only increased to about 91 percent.
Even at the least restrictive settings, certain search terms resulted in much more blocking — about 10 percent of health sites found by searches using the terms “safe sex,” “condom,” and “gay” were blocked.
Also using those terms, the percent of sites blocked at moderately restrictive settings was even higher; and at the most restrictive blocking setting, several of the more controversial search terms had blocking rates above 40 percent. — University of Michigan
