CAIRO — The big screen shows a man eyeing a middle-aged woman on a jam-packed bus and sliding up quietly behind her. Even before his hands reach for her hips, the young women watching in the darkened theater squirm in their seats.

They know the offending move all too well.

In overcrowded, male-dominated Cairo, four out of five Egyptian women say they’ve been brushed, rubbed, squeezed, teased, catcalled, trailed or otherwise treated inappropriately by strange men in public. Now, what experts describe as Egypt’s epidemic of sexual harassment is the subject of a new feature film that’s sparked debate over an everyday crime long shrouded in silence.

Released last month and inspired by true stories, the film is titled “678,” for the number of the bus that one of the main characters rides to work each morning, where she becomes the helpless object of lewd behavior.

Writer-director Mohamed Diab said the numerals also signified a problem that was increasing steadily as Egypt confronted a complex mix of social issues: economic stagnation, rising religious conservatism and changing attitudes about women and sex.

In the film, a mob of men assaults a jeweler outside a soccer game; afterward, her husband says he can’t bear to look at her.

A pretty young woman from a well-to-do family chases frantically after a truck driver who grabbed her breast as he drove past.

The two victims form an unlikely friendship with the working-class woman on the bus, and together they plot to exact violent revenge on Cairo’s men.

After a screening one recent afternoon at a Cairo shopping mall, a gaggle of college-age girls nodded enthusiastically when they were asked whether the stories rang true.

“It’s so real. I loved it so much,” gushed Nariman Farouk, a 20-year-old fine arts student.

“Every shot is real. Those things happen all the time,” Farouk said.

They happen so often, in fact, that she’s taken to carrying her keys in one fist when she walks through the city, the sharp metal edges ready to strike in case someone tries anything.

Experts say the phenomenon risks pushing women further into the shadows of Egyptian society.

In this proud, polyglot country of more than 80 million people, however, the film also drew criticism.

At least one lawsuit already has been filed against Diab, accusing him of inciting women to violence. Another accused him of sullying Egypt’s image; that suit was thrown out of court.

“I knew this would happen,” said Diab, a 33-year-old screenwriter with several blockbuster films to his credit. “It’s creating a huge debate, which is the reason I made the film: to break the silence.”

American moviegoers might recall “Disclosure,” the 1994 Hollywood film that featured Michael Douglas and Demi Moore in a he-said she-said battle over harassment allegations in a corporate executive suite.

n Egypt, sexual harassment is a street-level phenomenon that experts say is rooted in the shrinking public space for women, an idea that “678” drives home in every shot of a bus, market, stadium or theater filled with men.

In 2008, a survey by the Egyptian Center for Women’s Rights, an independent advocacy group, revealed a startling statistic: Eighty-three percent of Egyptian women reported that they’d been sexually harassed.

A majority of incidents aren’t physical, and very few are outright violent.

Most happen in a flash, women say: A man grabs you from behind on a busy street and disappears into the crowd, or he lets his hand linger for a moment as he brushes past.

While 53 percent of the men in the survey blamed women for “bringing it on” by wearing provocative clothes, the study showed that most incidents targeted women who were dressed modestly, often wearing the traditional Muslim head covering known as hijab.

In the film, harassers equally victimize veiled women and those in Western outfits; one of the characters goes jogging in a sweat suit through a tony Cairo suburb and elicits catcalls from passing cars.

“When I interviewed girls, I discovered that it doesn’t matter who you are, if you look good or not, if you’re covered or not,” Diab said.

 “If you’re a female, it’s going to happen to you.”

• Shashank Bengali