But that hasn't stopped thousands from finding their way into cyberspace. And a daring few post candid blogs about life in the communist-run country that have garnered international audiences.
Yoani Sanchez writes the "Generation Y" blog and gets more than a million hits a month, mostly from abroad - though she has begun to strike a chord in Cuba. On her site and others, anonymous Cubans offer stinging criticisms of their government.
But it isn't simple. To post her blog, Sanchez dresses like a tourist and slips into Havana hotels with Web access for foreigners. It costs about $6 an hour and she can't afford to stay long given the price and the possibility someone might catch her connecting without permission.
It's a testament to the ingenuity and black-market prowess Cubans have developed living on salaries averaging $20 a month, with constant restrictions and shortages.
The connections Cuban bloggers are making with the outside world via the Internet are irreversible, said Sanchez, who this month won the Ortega and Gasset Prize for digital journalism, a top Spanish media award.
"With each step we take in that direction, it's harder for the government to push us back," she said.
On an island where many censor themselves to avoid trouble, Sanchez says "Generation Y" holds nothing back.
"It's about how I live," she said. "I think that technically, there are no limits. I have talked about things like Fidel Castro, and you know how taboo that can be."
But she added that "there are some ethical limits. I would never call for violence, for instance."
Since taking over from his ailing brother Fidel in February, Raul Castro has lifted bans on Cubans buying consumer electronics, having cell phones and staying in luxury tourist hotels.
While the changes have bolstered the new president's popularity, most simply legalized what was common practice. In a typically frank recent posting, Sanchez noted that many Cubans already had PCs, cell phones and DVD players bought on the black market.
"Legally recognizing what were already facts prospering in the shadows is not the same as allowing or approving something," she wrote. Cuba's leaders are responding to the inevitable, "but they won't soothe our hunger for change."
Authorities have made no sustained effort to stop Sanchez's year-old blog, though pro-government sites accuse her of taking money from opposition groups.
Only foreigners and some government employees and academics are allowed Internet accounts and these are administered by the state.
Ordinary Cubans can join an island-wide network that allows them to send and receive international e-mail. Lines are long at youth clubs, post offices and the few Internet cafes that provide access, but the rest of the Web is blocked - a control far stricter than even China's or Saudi Arabia's.
Still, thousands of Cubans pay about $40 a month for black market dial-up Internet accounts bought through third parties overseas or stolen from foreign providers. Or they use passwords from authorized Cuban government accounts that hackers swipe or buy from corrupt officials.
Sanchez said so many Cubans read her blog that fans stop her on the street.
Generation Y takes its title from a Cuban passion for names beginning in Y. It offers witty and biting accounts of Cubans' everyday struggles against government restrictions at every turn.
Some of the bloggers hew to the belief that openness is the best answer to official surveillance.
"By signing your name, giving your opinions out loud and not hiding anything, we disarm their efforts to watch us," Sanchez wrote on her blog.
On a blog called "Without Evasion," Eva Hernandez dared to mock "Granma," the official Communist Party newspaper, for taking its name from the American yacht that brought Castro and his rebels back to Cuba from Mexico to launch their armed rebellion in 1956.
"Cuba is the only country in the world whose principal newspaper, the official organ of the Communist Party and the official voice of the government, has the ridiculous name 'granny,"' she wrote. Piling on the heat, she added that the name "perpetuates the memory of that yacht that brought us so much that is bad."
Generation Y is maintained by a server in Germany, and Sanchez says the Cuban government periodically attempts to block her site within Cuba, though the problem is always cleared up within hours.
Administrators of the "Petrosalvaje" site also claim to struggle with government-imposed limits. A recent post called uncensored Internet access a "virtual raft" - a reference to the rafts on which Cubans flee to the United States.
The government is also into blogging - maintaining dozens of sites dedicated to promoting the island's image overseas.
"Raul needs time," reads a post on Kaosenlared.net, a forum based in Spain. "We are confident, calm and staying united in favor of the direction of our revolution." It is signed Rogelio Sarforat and was apparently posted from Cuba.
Reynaldo Escobar, Sanchez' husband and a former journalist for official media, now uses his own blog to criticize the government. He said Cuba pays supporters to flood the Internet with positive opinions.
He says he knows of nobody who would spend money to go on the Web and defend the system. "Everyone who argues in favor of the government is paid to do so, or does so because they have been asked to," he said