WHAT do Barbra Streisand and the Tunisian president, Zine el-Abidine Ben Ali, have in common? They both tried to block material they dislike from appearing on the internet. And they were both spectacularly unsuccessful. In 2003 Ms Streisand objected to aerial photographs of her home in Malibu appearing in a collection of publicly available coastline pictures. She sued (unsuccessfully) for $50m—and in doing so ensured that the pictures gained far wider publicity.

That self-defeating behaviour coined the phrase “Streisand effect”, illustrated by an axiom from John Gilmore, one of the pioneers of the internet, that: “The Net interprets censorship as damage and routes around it.” But the big test of the rule is not whether it frustrates publicity-shy celebrities. It is whether it can overcome governments’ desire for secrecy.

In November 2007 Tunisia blocked access to the popular video-sharing sites YouTube and DailyMotion, which both carried material about Tunisian political prisoners. It was not for the first time, and many other countries have blocked access to such sites, either to protect public morals, or to spare politicians’ blushes. What was unusual this time was the response. Tunisian activists and their allies organised a “digital sit-in”, linking dozens of videos about civil liberties to the image of the presidential palace in Google Earth. That turned a low-key human-rights story into a fashionable global campaign.

It was the same story in Armenia in March, where the president, Robert Kocharian, ended his term in office with a media blackout that, supposedly, extended to blogs (self-published websites which typically contain the author’s personal observations and opinions). Like all other outlets, the authorities said, blogs could publish government news only. The result was a soaring number of blogs hosted on servers outside Armenia—all sharply critical of the authorities.

Some countries still think that the benefits of censorship are worth the opprobrium. China unabashedly blocks foreign news sites, with state-financed digital censors playing an elaborate game of cat and mouse with those trying to elude them. Saudi Arabia makes a positive virtue of the practice, warning those trying to access prohibited websites of the dangers of pornography: sources cited include the Koran and Cass Sunstein, an American scholar who argues that porn does not automatically deserve First Amendment protection.

Such authoritarian countries are increasingly co-operating: Chinese software for finding keywords and spotting dangerous sites is among the best in the world. But international co-operation cuts both ways. If Egypt, for example, buys Chinese web-censorship technology, the Egyptian bloggers may learn ways to bypass it from their Chinese colleagues before the technology arrives.

That may keep information flowing fairly freely. But it does not keep bloggers out of prison. Security officials who once scoffed at blogs, or ignored them completely in favour of bigger and more conspicuous targets, are now bringing their legal and other arsenals to bear. A common move is to expand media, information and electoral laws to include blogs. Last year, for example, Uzbekistan changed its media law to count all websites as “mass media”—a category subject to Draconian restriction. Belarus now requires owners of internet cafés to keep a log of all websites that their customers visit: in a country where internet access at home is still rare and costly, that is a big hurdle for the active netizen. Earlier this year Indonesia passed a law that made it much riskier to publish controversial opinions online. A Brazilian court has ruled that bloggers, like other media, must abide by restrictions imposed by the law on elections.

The chilling effect of such moves is intensified when governments back them up with imprisonment. From Egypt to Malaysia to Saudi Arabia to Singapore, bloggers have in recent months found themselves behind bars for posting materials that those in power dislike. The most recent Worldwide Press Freedom Index, published by Reporters Without Borders, a lobby group, estimates their number at a minimum of 64.

International human-rights organisations have taken up their cause. But the best and quickest way of defending those in prison may be with the help of other internet activists. Sami ben Gharbia, a Tunisian digital activist who now lives in exile in the Netherlands, says that this beats traditional human-rights outfits when it comes to informing the world about the arrest of fellow bloggers. He co-ordinates the campaigning efforts of Global Voices Online, a web-based outfit that began as a collator of offbeat blog content and has now branched out into lobbying for free speech.

Such issues were expected to be in sharp focus at Global Voices’ annual summit in Budapest this week, where hundreds of bloggers, academics, do-gooders and journalists from places like China, Belarus, Venezuela and Kenya were due to swap tips on how to outwit officialdom. The aim, says Ethan Zuckerman, a Harvard academic who cofounded Global Voices, is to build networks of trust and co-operation between people who would not instinctively look to the other side of the world for solutions to their problems.

That is a worthy if ambitious goal. Doubtless, authoritarian governments are in close touch too, sharing the best ways of dealing with the pestilential gadflies and troublemakers of the internet. But they will not be posting their conclusions online, for all to see. Which way works better? History will decide.

From The Economist print edition | Jun 26th 2008