(CBS News) CAIRO -- They came onto the square to demonstrate against the government, but this fight is not about politics. You can't see her, but there is a woman in the middle of the mob, and she is being assaulted. The fight between her attackers and those trying to rescue her is fierce: clubs are used, knives, even a makeshift blowtorch.
Filmmaker and activist Aida El Kashef made the video to show Egyptians what these mob attacks on women look like.
"It's not a fight, it's a girl inside, now their hands are in her pants, now they're doing this, now they're doing that," El Kashef says.
Asked why the police didn't intervene, she says, "I wouldn't trust a policeman saving me."
El Kashef says that 20 other women were assaulted that night. Sexual harassment has always been a part of life in Egypt, but before the revolution, there were few demonstrations, and mass sexual assaults were virtually unheard of. Not anymore.
Watch: Lara Logan breaks her silence on Tahrir Square assault, below.
El Kashef says there are women being assaulted at every protest.
"It's huge," she says. "It's basically -- it's something I've never seen before."
El Kashef and other activists decided to fight back. They formed teams that try to spot attacks as they happen, pushing their way in to rescue the victim.
"Basically, people just started grabbing me everywhere, trying to take off my clothes," she says. "My underwear was torn, and the thing is that it was not about the sexual assault at that moment, it's just that you're being pulled from every inch of your body."