By Clark Boyd
Technology correspondent, in Boston
A new book details the extent to which countries across the globe are increasingly censoring online information they find strategically, politically or culturally threatening.
China blocks many Western media websites
Access Denied: The Practice and Policy of Global Internet Filtering challenges the long-standing assumption that the internet is an unfettered space where citizens from around the world can freely communicate and mobilise. In fact, the book makes it clear that the scope, scale and sophistication of net censorship are growing.
"There's been a conventional wisdom or myth that the internet was immune from state regulation," says Ronald Deibert, one of the book's editors.
"What we're finding is that states that were taking a hands-off approach to the internet for many years are now finding ways to intervene at key internet choke points, and block access to information."
Mr. Deibert heads The Citizen Lab at the University of Toronto. The Lab, along with Harvard Law School, the University of Cambridge, and Oxford University, has spent the last five years testing internet access in some 40 countries.
The book highlights Saudi Arabia, Iran and China as some of the most aggressive nations when it comes to net filtering. They use a variety of techniques to limit what their citizens can see online. But they reinforce that filtering with other methods, such as net surveillance.
"Surveillance is a huge deterrent," says The Citizen Lab's Nart Villeneuve. "If you talk to dissident groups in these countries, they'll tell you that they're under surveillance, that they're concerned for their safety, and that it definitely influences their online behavior."
And even as human rights and internet rights groups fight to raise awareness about internet censorship, countries such as China have responded by getting smarter in what they block, and when they block it.
"We call it 'just-in-time' filtering," Mr. Deibert says. "Countries are selectively blocking access to information around key events, such as demonstrations or elections. They are clamping down on the internet during times that it suits their strategic interests to do so."
As an example of this kind of filtering, he points to China's recent blocking of YouTube after videos of Tibetan protestors appeared on the video-sharing site.
Google has been criticised for working with Chinese authorities
Belarus, Cambodia and Burma have all engaged in this kind of selective censorship as well.
And then there is the case of Pakistan, which recently caused the entire YouTube service to go down worldwide for a couple of hours because of a government order to block material.
According to John Palfrey, director of Harvard Law School's Berkman Center for Internet and Society, the Pakistan case points to certain weaknesses inherent in the very architecture of the internet.
"It was designed by a bunch of friends in essence - academics and military people - who were just creating a local network. Now, it has scaled globally.
"But it's still based on some fairly informal protocols. It turns out that when one censor in one country messes around with something, he can bring down access to entire parts of the internet."
Mr Palfrey points out that some countries are considering whether or not to bypass the World Wide Web all together by creating what amounts to their own local area networks. "We are starting to see something more like the China Wide Web, the Pakistan Wide Web, and the Iran Wide Web."
But The Citizen Lab's Ronald Deibert does not think the evidence points to a complete "balkanization" of the net by sovereign states.
"I don't think it's a stretch to say that a person in Iran experiences a much different Internet than a citizen in a country like Canada," he says.
"But it's not a simple equation with territorial boundaries. Maybe the best analogy is with the old Middle Ages, where you had multiple and overlapping layers of authority. I think that's the future of the net."
That future is being complicated by the increased use of mobile phones, PDAs and other devices to access information online. For citizens, these devices mean more ways to access the internet, and therefore more potential ways around government blocking.
But Jonathan Zittrain, chair in Internet Governance and Regulation at Oxford University, says that governments are already starting to realize the potential threats from mobile devices as tools to access and spread information.
"In fact, when it comes to mobile devices," Zittrain says, "you may see common cause among China, the United States and Europe, all of whom would like another lever they can pull that will enhance their control over the net, whether they're looking for terrorists, subversives or political dissidents."
"I'd hate to think that the technological advances, say, in America, turn out to be exactly the advances, wrapped in a bow, the technologies China might use to squash dissidents."