BEIJING — Since its first unheralded appearance in January on a Chinese Web page, the grass-mud horse has become nothing less than a phenomenon.

A YouTube children’s song about the beast has drawn nearly 1.4 million viewers. A grass-mud horse cartoon has logged a quarter million more views. A nature documentary on its habits attracted 180,000 more. Stores are selling grass-mud horse dolls. Chinese intellectuals are writing treatises on the grass-mud horse’s social importance. The story of the grass-mud horse’s struggle against the evil river crab has spread far and wide across the Chinese online community.

Not bad for a mythical creature whose name, in Chinese, sounds very much like an especially vile obscenity. Which is precisely the point.

The grass-mud horse is an example of something that, in China’s authoritarian system, passes as subversive behavior. Conceived as an impish protest against censorship, the foul-named little horse has not merely made government censors look ridiculous, although it has surely done that.

It has also raised real questions about China’s ability to stanch the flow of information over the Internet — a project on which the Chinese government already has expended untold riches, and written countless software algorithms to weed deviant thought from the world’s largest cyber-community.

Government computers scan Chinese cyberspace constantly, hunting for words and phrases that censors have dubbed inflammatory or seditious. When they find one, the offending blog or chat can be blocked within minutes.

Xiao Qiang, an adjunct professor of journalism at the University of California, Berkeley, who oversees a project that monitors Chinese Web sites, said in an e-mail message that the grass-mud horse “has become an icon of resistance to censorship.”

“The expression and cartoon videos may seem like a juvenile response to an unreasonable rule,” he wrote. “But the fact that the vast online population has joined the chorus, from serious scholars to usually politically apathetic urban white-collar workers, shows how strongly this expression resonates.”

Wang Xiaofeng, a journalist and blogger based in Beijing, said in an interview that the little animal neatly illustrates the futility of censorship. “When people have emotions or feelings they want to express, they need a space or channel,” he said. “It is like a water flow — if you block one direction, it flows to other directions, or overflows. There’s got to be an outlet.”

China’s online population has always endured censorship, but the oversight increased markedly in December, after a pro-democracy movement led by highly regarded intellectuals, Charter 08, released an online petition calling for an end to the Communist Party’s monopoly on power.

Shortly afterward, government censors began a campaign, ostensibly against Internet pornography and other forms of deviance. By mid-February, the government effort had shut down more than 1,900 Web sites and 250 blogs — not only overtly pornographic sites, but also online discussion forums, instant-message groups and even cellphone text messages in which political and other sensitive issues were broached.

Among the most prominent Web sites that were closed down was bullog.com, a widely read forum whose liberal-minded bloggers had written in detail about Charter 08. China Digital Times, Mr. Xiao’s monitoring project at the University of California, called it “the most vicious crackdown in years.”

It was against this background that the grass-mud horse and several mythical companions appeared in early January on the Chinese Internet portal Baidu. The creatures’ names, as written in Chinese, were innocent enough. But much as “bear” and “bare” have different meanings in English, their spoken names were double entendres with inarguably dirty second meanings.

So while “grass-mud horse” sounds like a nasty curse in Chinese, its written Chinese characters are completely different, and its meaning —taken literally — is benign. Thus the beast not only has dodged censors’ computers, but has also eluded the government’s own ban on so-called offensive behavior.

As depicted online, the grass-mud horse seems innocent enough at the start.

An alpaca-like animal — in fact, the videos show alpacas — it lives in a desert whose name resembles yet another foul word. The horses are “courageous, tenacious and overcome the difficult environment,” a YouTube song about them says.

But they face a problem: invading “river crabs” that are devouring their grassland. In spoken Chinese, “river crab” sounds very much like “harmony,” which in China’s cyberspace has become a synonym for censorship. Censored bloggers often say their posts have been “harmonized” — a term directly derived from President Hu Jintao’s regular exhortations for Chinese citizens to create a harmonious society.

In the end, one song says, the horses are victorious: “They defeated the river crabs in order to protect their grassland; river crabs forever disappeared from the Ma Le Ge Bi,” the desert.

The online videos’ scenes of alpacas happily romping to the Disney-style sounds of a children’s chorus quickly turn shocking — then, to many Chinese, hilarious — as it becomes clear that the songs fairly burst with disgusting language.

To Chinese intellectuals, the songs’ message is clearly subversive, a lesson that citizens can flout authority even as they appear to follow the rules. “Its underlying tone is: I know you do not allow me to say certain things. See, I am completely cooperative, right?” the Beijing Film Academy professor and social critic Cui Weiping wrote in her own blog. “I am singing a cute children’s song — I am a grass-mud horse! Even though it is heard by the entire world, you can’t say I’ve broken the law.”

In an essay titled “I am a grass-mud horse,” Ms. Cui compared the anti-smut campaign to China’s 1983 “anti-spiritual pollution campaign,” another crusade against pornography whose broader aim was to crush Western-influenced critics of the ruling party.

Another noted blogger, the Tsinghua University sociologist Guo Yuhua, called the grass-mud horse allusions “weapons of the weak” — the title of a book by the Yale political scientist James Scott describing how powerless peasants resisted dictatorial regimes.

Of course, the government could decide to delete all Internet references to the phrase “grass-mud horse,” an easy task for its censorship software. But while China’s cybercitizens may be weak, they are also ingenious.

The Shanghai blogger Uln already has an idea. Blogging tongue in cheek — or perhaps not — he recently suggested that online democracy advocates stop referring to Charter 08 by its name, and instead choose a different moniker. “Wang,” perhaps. Wang is a ubiquitous surname, and weeding out the subversive Wangs from the harmless ones might melt circuits in even the censors’ most powerful computer.