(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."
Mahmoud Osman volunteers with a group called Tahrir Bodyguards, who wear fluorescent jackets and helmets that are easy to spot in the crowd.
"Definitely we get beaten, and not just by hands," he says. "We wear helmets, and if it wasn't for those helmets, I would probably be having a concussion by now, lying in some ICU."
Activists complain that Egypt's new government has done nothing to make the streets safer for women. So the Bodyguards also offer self-defense classes, and El Kashef says she and her friends carry electric prods and knives to protect themselves.
Watch: Clarissa Ward reports on Egyptian women sexually assaulted by military, below.
"It's the only way," she says. "You're being attacked daily, and with mass numbers. What else can you do?"
Asked whether she sometimes thinks her presence is more of a hindrance than a help, El Kashef replies, "It is our fight as women."
"Men are welcome to help, of course, but it is our fight," she adds.
A fight they won't give up.