Since its advent, people have been trying to censor the Internet. And growing with these censorship attempts is the debate over the effectiveness of filtering software, a tool used to 'filter out' material deemed inappropriate by schools, libraries, businesses and parents.   Traditional filtering software provides the user with a list of words that identify sites containing that word. All Web sites containing the word 'sex,' for example, would be blocked out by the computer when that word is typed in. The user would then be given the names of these sites to add to a master list of blocked sites.   The problem has been that this software blocks many useful sites -- for example, sites dealing with sexual harassment -- along with those of 'questionable' material. Another limitation is that with the constant growth of the Internet, it is impossible to manage a master list daily.   And parents who purchase filtering software are concerned that its design allows it to be disabled easily, sometimes only with a simple keyword search.   So, what is the future of Internet filters? Should we abandon them because they are not 100 percent effective?   Developers at UR Labs in Hampton, Va. have taken a new approach to Internet filtering. By using a content-based search, I-Gear software not only looks for the specified word but also its overall context in the Web page. Therefore, a site containing government laws on gambling would not be screened out if a parent had restricted access to gambling sites, as it would be with traditional filters.   Dan Sydow, vice president of business development, said that I-Gear can also look at the semantics of the page in screening out material, as well as read metatags (pieces of code in some Web pages that provide information to search engines) and adverbs. The software also reads content in Spanish and other languages. 'We are applying real technology to help solve these issues,' he said.   The software also allows for greater flexibility, as parents can assign individual user permissions to their children to take with them on diskette wherever they go. This leaves the argument of libraries restricting free speech with Internet filters in the dust, because individual users or their parents can choose their own criteria.   'We are very excited about this new technology,' said Sydow. 'We can offer filtering to a parent without affecting others.'   UR Labs is working with Internet service providers to make the software available to the individual user.   Landmark Communications, Inc., is also working to increase the intelligence of Internet filters. The Norfolk, Va.-based company surveyed parents' concerns about the Internet in December, 1997, and found that about 75 percent were worried about what their children are exposed to on the Internet.   GuardiaNet, a server-based application, is a content-oriented Web 'crawler' that uses phrases to categorize Web sites, and constantly seeks out 'inappropriate' web sites and updates itself.   The software is protected by a firewall, a security feature that sits in front of the server to prevent its content from being modified.   Landmark President Doug Young said he hopes that parents take advantage of these new advances in light of research that shows a 75 percent annual growth in Internet filter use. 'I hope and would expect that more and more households take advantage of this tremendous medium,' he said.   Internet expert and children's advocate Jean Armour Polly is happy to see the advances in Internet filtering techniques but believes the interest parents take in their children's Internet education is crucial. 'The most important thing is for parents to spend time with their kids on the Internet,' said Polly.