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Linguist Nunberg discusses problems of Internet filters

Of all the "rotten information" floating around the Internet graphic violence, racism, pirated software, term papers for sale, incorrect facts, bomb-making instructions pornography has spawned the most hysteria, according to Geoffrey Nunberg, a senior researcher at Stanford's Center for the Study of Language and Information. But Internet filters regularly snag protected speech as well as smut, Nunberg said.

At Thursday's Symbolic Systems Forum, the linguist discussed the social, legal and technological issues raised during a recent court challenge to the federal Children's Internet Protection Act (CIPA). His presentation was titled "Faulty Filters: What to Do About 'Rotten Information' in the Digital Age?"

Nunberg served as an expert witness for the American Library Association and other plaintiffs, including the public libraries of Multnomah County in Oregon, the American Civil Liberties Union and a variety of websites and library patrons, that argue CIPA is unconstitutional on First Amendment grounds.

In March, the case was heard by a three-judge panel for the U.S. Court of Appeals for the Third Circuit.

Government lawyers, while conceding problems with Internet filters, maintained that, in accordance with CIPA, the software blocked the majority of obscene web pages. The government also argued that since book stacks in public libraries are generally free of pornography, people should not have access to it via library computers.

The libraries argued that filters inevitably block at least some constitutionally protected speech, which constitutes "prior restraint" -- censorship of speech before it has undergone judicial review. They also argued that the Internet constitutes "an open public forum" and as such cannot be treated as a traditional library.


Filtering technology

A frenzied search for technological solutions to the problem of smut in cyberspace began about five years ago, and companies that make filters haven't been shy about leveraging this anxiety to boost sales, Nunberg said.

Meanwhile, Congress has passed several laws attempting to shield the eyes of young web surfers from X-rated material online. The first was the Communications Decency Act, which was voted into law in 1996 but struck down the following year by the Supreme Court. CIPA, which was signed into law by former President Clinton shortly before he left office, is only the most recent legislative attempt. It requires public schools and libraries to install a "technology protection measure," such as an Internet filter, to guard against depictions that are obscene, contain child pornography or are harmful to minors. Failure to comply means the loss of federal subsidies for Internet use.

There are two types of Internet filters: database filters, which compare the uniform resource locator (URL) or Internet protocol (IP) address to a control list; and dynamic filters, which look at the content of a web page in real time and rely on word lists and algorithms to determine whether a page should be blocked.

Dynamic filters catch more but overblock more; database filters are more precise but miss a lot, and they sometimes block websites at their root URLs. Thus, some filters might block all of, including interviews and consumer information "and other things that are not only protected speech but conceivably useful," Nunberg said.

It becomes even more problematic when a filter blocks an IP address, which may host a pornographic magazine but also, say, a children's soccer league website, Nunberg said. The URLs may differ, but both sites are clients of the same virtual host.

When Nunberg and others involved in the case examined libraries' Internet logs, they found that 6 to 10 percent of websites listed had been inappropriately blocked by filters. "That's a big number, particularly when you consider how many sites are on the web," he said.

In May, the three-judge panel ruled overwhelmingly in favor of the American Library Association et al. The court argued that the technology would violate the First Amendment rights of library patrons by blocking too much acceptable material. The government has appealed the decision, and the case is scheduled to go before the Supreme Court on March 5.

The Symbolic Systems Forum, a weekly series, is held at 4:15 p.m. Thursdays in Room 380C of Building 380 (Math Corner). On Thursday, Jan. 16, the speaker will Nils Nilsson, the Kumagai Professor in the School of Engineering, Emeritus, who will present a talk titled "Considerations Regarding Human-Level Artificial Intelligence."


By John Sanford

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