Consumer Reports' research shows filtering software effectively blocks porn sites, but not sites that promote hate, violence and drugs. And even the best of today's safeguards tend to block educational sites they shouldn't.

A recent study by the Pew Internet & American Life Project says almost 19 million American children between the ages of 12 and 17 can access the Internet at home. Besides the many pornographic sites that litter the Net, there now are more than 5,000 hate-promoting sites — up 25 percent from last year, according to the Simon Wiesenthal Center.

So Internet filtering software is more important to parents than ever.

The software works by inserting itself between your computer's browser and Internet connection to prevent objectionable sites from getting through.

Consumer Reports tested the effectiveness of 11 filtering products (including the filters built into online services AOL and MSN). As part of the test, CR built a list of objectionable sites that anyone can easily find, plus informational sites to test the filters' ability to discern the objectionable from the merely sensitive. CR configured each filter as it would be configured by the parent of a 12- to 15-year-old, then tried to access the sites.

Among the results:

• Porn sites: All the tested products were very good or excellent at blocking pornography. KidsNet, a software product that costs $60 to buy and $60 annually to use after the first year, joined the Parental Controls supplied with AOL and MSN online services in blocking practically every site in our test.

• Hate sites: The filters had a tough time blocking hate sites and those advocating illegal drug use, violence and weapons-making. Of 11 products tested, only AOL and KidsNet succeeded in blocking a site that detailed how to kill someone with your bare hands.

• Useful sites: The best porn blockers were heavy-handed against sites about health issues, sex education, civil rights and politics. For example, seven products blocked KeepAndBearArms.com, a site advocating gun owners' rights. Four products blocked the National Institute on Drug Abuse, part of the federal government's National Institutes of Health. KidsNet interfered the most with useful sites, blocking 73 percent.

• Overall best: One product stood out as best for most people. SafeBrowse.com's Safe Eyes 2005 ($50, with no annual fee) offers the best combination of protection and minimum interference, and is one of the few programs that interfered minimally with search-engine results. (Several products blocked the entire results page of a Google or Yahoo search if some links had objectionable words in them.) It also features many filtering categories and age levels for Web sites, plus controls for time management (it lets you set up time limits for Internet use), e-mail, instant messaging, personal information and other applications such as games. But it is not Macintosh-compatible.

• Best for Mac users or families with young kids: AOL's Parental Controls 9.0. This feature comes free with AOL service, and offers the best pornography blocking and time-management controls. Like all Mac-compatible products tested, however, it couldn't filter effectively without interfering substantially with legitimate sites.

Copyright 2005, Consumers Union

More on protecting kids online

Resources: American Library Association at www.ala.org/ala/pio/availablepiomat/safetytips.htm; www.netparents.org; www.kids.getnetwise.org; and "A Parent's Guide to Internet Safety" at www.fbi.gov/publications.htm.