South Korea's approach also speaks to the growing sophistication of the filtering employed by countries. Gone are the days when filtering one blog or one website necessarily meant shutting down, say, all of Blogspot, or an entire domain.

"In the early days, countries used relatively crude blocking mechanisms at the national backbone level, or imposed restrictions upon ISPs that were applied in uneven ways," says Ronald Deibert, director of the Citizen Lab. "Now we see first and foremost that many countries are using commercial filtering technologies, most of which are made by U.S. companies. That's providing them with a finer-grain level of service."

Many countries are also getting better at homegrown filtering, according to the report. Five years ago, most countries would only block English-language material deemed offensive. But as more content has been created in local languages, the report concludes, repressive regimes have had to tweak their filtering technology to keep up.

Deibert also notes that ONI found evidence that filtering has moved beyond websites and into applications. Some nations now block access to programs such as Google Maps and the voice-over-Internet application Skype. Thailand recently blocked access to the video-upload site YouTube.

But most pernicious, Deibert says, is something he calls "event-based" filtering, of which Belarus provides an interesting example. Before the elections in March of 2006, Deibert notes, Belarus wasn't blocking Internet content by technical means. Instead, the country's strict laws regarding online content kept many Belarusians critical of the government in check.

Then, at the time of key moments in the election, ONI realized that opposition websites were suddenly inaccessible inside the country. This led Deibert to believe that for just this brief period of time, laws designed to promote self-censorship weren't enough. The government had indeed started blocking content.

"This is a harbinger of what's to come worldwide," Deibert says. "You'll have filtering just during critical times, such as elections. Countries realize they risk becoming pariahs, and so they'll find more surreptitious ways of filtering."

Cambodia recently took this kind of censorship beyond the confines of the computer, when it ordered that cell-phone text-messaging services be cut off during elections. ONI is already thinking of ways to incorporate this kind of filtering into future studies.

"We're going to have to keep an eye not just on the network, but on the endpoint," says Jonathan Zittrain, professor of Internet governance and regulation at Oxford University, "because the device you use and how it works, whether it's a computer or, say, a Blackberry, will have a huge impact on what you can do or not do on the Net, and how easily you can be monitored."