A comprehensive U-M 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. Setting Internet filters to their most restrictive level, however, prevents computer users from seeing many health sites — and gives only marginally better protection against pornography than the least restrictive setting.

Caroline Richardson Photo: Gregory Fox

Researchers in the U-M Medical School and School of Information used 24 health search terms and six pornographic terms to compare the Internet search performance of pornography-blocking software filters. Results of the study were published in the December 11, 2002, issue of the Journal of the American Medical Association.

“We found that filters, when set at the least restrictive setting, were remarkably good at distinguishing between health information and pornography. At highly restrictive settings, however, almost a quarter of health sites were blocked with little improvement in porn blocking,” says Caroline R. Richardson, M.D., a lecturer in family medicine and a research scientist at the Veterans Administration Health Services Research and Development Service in Ann Arbor.

Working with Paul J. Resnick, Ph.D., an associate professor in the U-M School of Information, and colleagues from the U-M Health Media Research Laboratory and the Kaiser Family Foundation, Richardson conducted the study with an eye toward teens who often turn to the Internet for health and sexuality information on issues such as pregnancy, sexually transmitted diseases and birth control.

The research team used six search engines popular with teens — Yahoo!, Google, America Online (AOL), Microsoft Network (MSN), Ask Jeeves and Alta Vista. They tested six commercial software packages, all widely used by schools and libraries. More than 3,000 health and 500 pornography sites were ultimately tested against 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. But at the most restrictive settings, which barred a broad range of categories, the blocking of health sites reached an average of 24 percent, while pornography blocking increased only to 91 percent.

The study was funded by the Kaiser Family Foundation. In addition to Richardson and Resnick, the study’s co-authors include senior author and Kaiser Family Foundation Vice President Vicki Rideout; Holly Derry, U-M Health Media Research Laboratory; and Derek Hansen, Ph.D., a graduate student in the School of Information.

—KG

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An executive summary of the study and complete results are available on the Kaiser Family Foundation’s Web site.