Politics aside, the Occupy Wall Street movement has given us some memorable imagery: electric-blue tarps, various graphic riffs on 99 percent, the hipster cop.

But in this new iconography, one image has emerged as particularly bedeviling (and just in time for Halloween): a grinning, somewhat sinister mask of the English folk hero Guy Fawkes.

The stark-white mask, with a Mephistophelian upturned mustache and dagger-thin goatee, was worn by V, the faceless leader in the comic book "V for Vendetta," who overthrows a future totalitarian society. The anti-establishment message has been embraced by the Wall Street occupiers.

On a blustery afternoon at Zuccotti Park last week, as spindly trees bent ghoulishly in the wind, a half-dozen occupiers wore the mask. "This is a leaderless movement," said Julio Rolon, a 36-year-old chef from Puerto Rico, who wore the mask, like many people, on the back of his head. "People in power don't know who they're going to have to take down first."

The mask has also been spotted at Occupy protests worldwide, including in London, where Julian Assange showed up wearing one but was told by the police to remove it under British laws banning public anonymity; in Paris, where masked protestors converged; and in Hong Kong, where protesters strung the mask on the bronze bull outside the stock exchange.

Plastic versions of the masks have been widely available since the comic book was made into a movie in 2006. But it was the "hacktivist" collective, Anonymous, that imbued it with real-life symbolism. Hackers, seeking to protect their identity, donned the masks whenever they appeared in public, including protests against the Church of Scientology.

The face behind the mask has an appropriately subversive story. Guy Fawkes was an Englishman who tried to blow up the House of Parliament in the early 17th century as part of a plot to give Catholics more power amid a Protestant monarchy. He failed, then killed himself to avoid execution, but became a British folk hero whose effigy is burned each Nov. 5, Guy Fawkes Day, a rough British counterpart to Halloween.

David Lloyd, a British comic book artist who illustrated "V for Vendetta," said that he didn't intend the mask to look sinister, but conceded that "it's a great symbol of protest for anyone who sees tyranny."

"The smile on its face is a happy accident," he said. "It represents inviolable optimism."

But Susan Hilferty, a costume designer who has designed masks for Broadway productions, including "Wicked," said that the Guy Fawkes mask has elements that link it to traditional visions of evil. "The stark black and white, the angularity, the gleam in the eye," she said. "We associate those with the Joker from 'Batman' and the Evil Queen from Disney's 'Snow White.' "

But, she added, "a sea of protesters wearing Porky Pig masks would be quite sinister, too."

Except, maybe, on Halloween, when a sea of Guy Fawkes masks is expected. The mask ($9.99) is one of the top sellers at Ricky's, the cosmetics chain in New York City that has several Halloween pop-up stores. At a distant second is the generic "mystery mask," said José Liriano, a store manager.

Meanwhile, the protesters at Zuccotti Park have found other practical uses for the masks. "If you want to show your support but are afraid you'll lose your job, just wear a mask - any mask," said Sid Hiltunen, 34, of White Plains, an unemployed former stockbroker.

Mr. Hiltunen added that he wears his Guy Fawkes mask all the time, except when sleeping or eating.

Guy Fawkes Mask Is Big on Wall Street & Halloween