They've tried everything to censor coverage, from banning reporters to shutting down Web sites.
But the news is still getting out, thanks, in part, to computer wizards half a world away, reports CBS News correspondent John Blackstone.
Miami, Okla. may be a small town far from anywhere, but for protesters in Iran marching again today in spite the increasingly tough government crackdown, the Oklahoma town has been a gateway to the rest of the world - by way of Anthony Papillion's computer.
"I always like to think I'm a techie with an activist heart," said Papillion, an Internet activist.
Papillon turned his computer into what's called a "proxy server."
"Basically a proxy server is a go-between between one computer and another," he said.
It's how one American and his computer can help Iranians get around government censors.
"So it's a crazy situation," Papillon said, "unimaginable here in the United States."
The censors in Iran have blocked access to popular web sites like Twitter, YouTube and Facebook. But by rerouting internet traffic to sites unknown to the censors, proxy servers let Iranians hide their real on line destination.
"As long as you can connect to the Internet, you can have a voice and you can make a huge difference on a global scale," Papillon said.
Iranians are using services like Twitter to talk to the world - and to each other. On Twitter today there are calls to gather: "Freedom loving Iranians needed in Haft-e-Tir Square," said one message. Another: "Go help your freedom fighters brave souls of Iran."
The video from Iran is reminiscent of demonstrations in China's Tiananmen Square 20 years ago. One of those demonstrators was Shiyu Zhou. Now he's a computer scientist in the U.S. working to keep the Internet open for Iranians.
"We do want to help people in closed societies and we understand their pain so we want to help them," Zhou said.
Zhou is among a group of Chinese exiles, computer engineers who created "Freegate" - software designed to help people in China dodge Internet censorship. But now Freegate is being used by some 400,000 people a day in Iran to beat government censors.
"The Iranian traffic to our platform exceeded the Chinese traffic," Zhou said.
Anthony Papillion's proxy server now appears to have been blocked by Iran's government, but he knows others are taking his place.
"I think the world is showing them that through technology everyone's equal," Papillon said.
As the Iranian government discovers and blocks proxy servers, communicating from the locked-down country has become an online game of cat-and-mouse - in which the mouse has become a powerful weapon.