Technology: Internet Filtering Processes

Internet censorship used to be pretty easy to spot. When China blocks YouTube or prohibits anything on the 1989 Tiananmen Square massacre, it's not hard to figure out what's going on. But as governments and commercial firms get savvier about the Internet, censorship is getting more subtle. A slow Web site could be an accidental glitch or something more intentional.

A new Web site now promises to add some much-needed data to what's so far been mainly anecdotal evidence. The Berkman Center for Internet and Society at Harvard University has for years produced reports on filtering practices by country. In March it launched Herdict (a combination of "herd" and "verdict"), a Web site that uses the power of crowd sourcing to produce just-in-time data about what's blocked and what's not. Users report sites that are unavailable or slow. This information appears in Herdict's "herdometer"—a kind of annotated map of the world that reveals online censorship as it unfolds. Incoming reports pop up in windows across the map.

When China (once again) began blocking YouTube back in March over video of Tibetan protests, Herdict was among the first to know as reports came flooding in from the field. Another test came in March, when the popular muckraking Web site Wikileaks landed on Australia's list of censored sites. Wikileaks became suspiciously inaccessible for a few hours that same week. Users from across the world barraged Herdict with hundreds of reports. As it turned out, Wikileaks was down for maintenance—but the false alarm served as proof of the integrity of Herdict's reporting system.

Herdict's creator, Jonathan Zittrain, believes that the Web site will help uncover subtle forms of censorship in the West—not by governments, but by commercial firms. Internet service providers and Web sites are continually making decisions about what makes it onto the Internet and what doesn't—largely behind closed doors, and not always in the public interest. In Britain, for instance, service providers formed the Internet Watch Foundation, a private nonprofit that informs them of which sites host online gambling, hate speech and child pornography. This self-policing has headed off legislation, but very little is known about what lands on Internet blacklists.

Activists worry that such unmediated systems for monitoring the Web can be abused, mainly by mission creep, and that the public would be none the wiser. "Once you've built that infrastructure," says Zittrain, "you see it starting to get used for other things." ISPs in several countries, including Britain, have already begun blocking the Pirate Bay, the well-known Swedish file-sharing site in Stockholm, whose founders were handed prison sentences in April for stealing intellectual property. But they've appealed, arguing that they were only serving as a directory for downloading sites and thus weren't breaking the law; last year ISPs won a ruling in Italy against the music industry.

It's still early, but Herdict may also detect if and when service providers begin violating "Net neutrality" rules by restricting or slowing down access to Web sites depending on which ones they do business with. Herdict is also good at revealing cases of geolocational filtering, such as when YouTube blocks content critical of Thai royalty specifically in Thailand. One of the most inaccessible sites, Herdict has found, is the Australian Broadcasting Corp., which, for copyright reasons, prevents users outside Australia from viewing videos online. In time, Herdict may wake up Westerners to the censorship in their backyards.

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