Burma, which was named the world’s worst place to be a blogger in a 2009 survey by the Committee to Protect Journalists (CPJ), broadly restricts Internet access, forcing people to access the Web through cyber cafés, which are carefully monitored. Bloggers caught disseminating damaging information have been severely punished. The comedian Muang Thura, for instance (better known as Zarganar, or “tweezers”), is serving a thirty-five-year sentence for distributing video of relief workers assisting the victims of Cyclone Nargis.

In Cuba, Internet access is officially restricted to government officials and members of the Communist Party, but a handful of independent bloggers operate in the country, using Internet cafés to access the Web. For the most part, Cuban authorities tolerate this because the bloggers don’t directly challenge the government and because their work is generally available only outside the island.

Blocking or severely limiting access to the Web, however, comes with a high economic and political cost. Governments that don’t let their citizens online are among the world’s most repressive; increasingly, a country cannot be part of the global economy without an information-based society. Countries like China and Iran take a more sophisticated approach, allowing broad access to the Internet but limiting the dissemination of certain kinds of critical content. This requires manpower and technology. In China, for example, an army of tens of thousands of Internet monitors scrutinizes the Web and removes “objectionable” content. The government blocks individual Web sites and key-word searches, monitors the use of certain terms (“Falun Gong,” “Tiananmen Square”), and arrests those who post commentary critical of the regime. In one recent case, the dissident poet Liu Xiaobo was sentenced on Christmas Day to eleven years in prison for “inciting subversion of state power.”

But China also understands that broad Web and cellular access—China has more online users than any other country—is necessary for global business. Most Chinese citizens operate happily inside a “walled garden,” where they are permitted to peruse a variety of information and even post certain kinds of critical comments. According to Rebecca MacKinnon, a China expert who is writing a book on the subject, most people in China lack the technical means or the even the interest to access blocked news sites, like the BBC Chinese service or YouTube. China is also putting pressure on the Internet Service Providers (ISPs), requiring them to serve as surrogate censors.

Iranians, too, have had broad access to the Web, a technology that has been embraced by the country’s conservative leadership, many of whom host blogs and Twitter. But Iran’s Internet connection to the world is in the hands of Telecommunications Company of Iran, a company in which a consortium associated with the Revolutionary Guards recently bought a 50 percent stake. Cyrus Farivar, a San Francisco-based tech journalist and Iran expert, calls control of the Internet “the biggest weapon in the government’s arsenal.” The number of international gateways that allow Internet traffic to enter or exit Iran is in the “single digits,” according to Farivar.

Restrictions of online content are not limited to repressive countries. Germany, for example, bans Holocaust deniers and neo-Nazis and requires Internet companies like Google and Yahoo to comply with government regulations. In India, according to a recent piece in The Wall Street Journal, Google has been forced to remove or censor content that could offend religious minorities or powerful political figures. The big fear of press-freedom advocates is creeping censorship under the guise of law enforcement or anti-pornography legislation.

Governments can also attack the third part of the information assembly line, blocking people from accessing certain kinds of information on the Web. Many repressive governments—including Iran, Tunisia, Saudi Arabia, Ethiopia, and China—use filters to block critical Web sites, a process known as blacklisting. Whitelisting, which is also widely practiced, refers to authorizing approved Web sites and blocking the rest. Increasingly, governments also require Internet café owners to police the sites that their clients visit; some have installed software that allows the government to do this remotely.

Joel Simon is the executive director of the Committee to Protect Journalists.