Freegate amounts to a dissident’s cyberkit. E-mails sent with it can be encrypted. And after a session is complete, a press of a button eliminates any sign that it was used on that computer.

Image Nicholas D. Kristof Credit... Fred R. Conrad/The New York Times

The consortium also makes available variants of the software, such as Ultrasurf, and other software to evade censors is available from Tor Project and the University of Toronto.

Originally, Freegate was available only in Chinese and English, but a growing number of people have been using it in other countries, such as Myanmar. Responding to the growing use of Freegate in Iran, the consortium introduced a Farsi-language version last July  and usage there skyrocketed.

Soon almost as many Iranians were using it as Chinese, straining server capacity (many Chinese are wary of Freegate because of its links to Falun Gong, which even ordinary citizens often distrust). The engineers in the consortium, worrying that the Iran traffic would crash their servers, dropped access in Iran in January but restored it before the Iran election.

“We know the pain of people in closed societies, and we do want to accommodate them,” Mr. Zhou said.

China is fighting back against the “hacktivists.” The government has announced that new computers sold beginning next month will have to have Internet filtering software, called Green Dam (the consortium has already developed software called Green Tsunami to neutralize it). More alarming, in 2006 a consortium engineer living outside Atlanta was attacked in his home, beaten up and his computers stolen. The engineers behind Freegate are now careful not to disclose their physical locations.

Granted, these technologies are not a panacea. One Chinese journalist estimated that only 5 percent of the country’s Netizens use proxy software, and the Iranians themselves managed a grass-roots revolution in 1979 without high-tech help. And at the end of the day, bullets usually trump tweets.