"Sokwanele" means "enough is enough" in a certain Bantu dialect. It is also the name of a Zimbabwean pro-democracy website whose bloggers last year published accounts of atrocities by Robert Mugabe's regime and posted Election Day updates describing voter intimidation and apparent ballot stuffing. You can visit Sokwanele's "terror album" and see photographs: of a hospitalized 70-year-old woman who'd been beaten and thrown on her cooking fire (she later died, the site says); of firebombed homes; of people with deep wounds carved into their backs. You can find detailed, frequently updated maps describing regional violence and other incidents. You will be confronted with gruesome news, starkly captioned: "Joshua Bakacheza's Body Found."

Because this horrific content is so readily available, it is easy to overlook the courage it took to produce it. The anonymous photographers and polling-station bloggers who uploaded the Sokwanele material remain very much in danger. In a place like Zimbabwe, where saying the wrong thing can get you killed or thrown in prison on treason charges, you take precautions: you're careful about whom you talk to; you're discreet when you enter a clinic to take pictures. And when you get to the point of putting your information on the Internet, you need protection from the possibility that your computer's digital address will be traced back to you. Maybe, at that point, you use Tor.

Tor is an open-source Internet anonymity system--one of several systems that encrypt data or hide the accompanying Internet address, and route the data to its final destination through intermediate computers called proxies. This combination of routing and encryption can mask a computer's actual location and circumvent government filters; to prying eyes, the Internet traffic seems to be coming from the proxies. At a time when global Internet access and social-networking technologies are surging, such tools are increasingly important to bloggers and other Web users living under repressive regimes. Without them, people in these countries might be unable to speak or read freely online (see "Beating Surveillance and Censorship").

Unlike most anonymity and circumvention technologies, Tor uses multiple proxies and encryption steps, providing extra security that is especially prized in areas where the risks are greatest. Paradoxically, that means it's impossible to confirm whether it's being used by the Zimbabwean bloggers. "Anyone who really needs Tor to speak anonymously isn't going to tell you they use Tor to speak anonymously," says Ethan Zuckerman, cofounder of Global Voices, an online platform and advocacy organization for bloggers around the world. "You can't tell if it's happening, and anyone who is actively evading something isn't going to talk about it." That said, the ­Sokwanele journalists "are extremely sophisticated and use a variety of encryption techniques to protect their identity," he says.

Anonymity aside, Internet users in dozens of countries--whether or not they are activist bloggers--often need to evade censorship by governments that block individual sites and even pages containing keywords relating to forbidden subjects. In 2006, the OpenNet Initiative--a research project based at Harvard and the Universities of Toronto, Oxford, and Cambridge that examines Internet censorship and surveillance--discovered some form of filtering in 25 of 46 nations tested, including China, Saudi Arabia, Iran, and Vietnam.

In a new and still-evolving study, OpenNet found that more than 36 countries are filtering one or more kinds of speech to varying degrees: political content, religious sites, pornography, even (in some Islamic nations) gambling sites. "Definitely, there is a growing norm around Internet content filtering," says Ronald Deibert, a University of Toronto political scientist who cofounded OpenNet. "It is a practice growing in scope, scale, and sophistication worldwide."