In most countries around the world, grandmothers settle for a life of relaxation and leisure after their retirement. In an impoverished area in Kenya, however, old women do not spend their time relaxing or having fun.

Instead, grandmothers in Korogocho slums in Nairobi spend hours learning how to defend themselves against the most unimaginable threat: young men who believe that raping older women will bring them some kind of cleansing after committing a crime.

"Boys had crazy ideas that after a robbery, when they sleep with an old woman, it's like they are cleansed," Sheila Kariuki, a former resident of Korogocho, explained.

"The young boys would strangle them ... Every time we went to pick up the corpse of an old woman, my heart used to bleed," she added.

Kariuki is now part of a charity called Ujamaa which launched a self-defence program to help older women fight the threats of rape. The program seeks to address the alarming number of rape incidents in the slums, which averages two or three elderly women per month.

The self-defence program, called "cucus" which means grandmas in the local Kikuyu language, now teaches more than 200 elderly women—some even reaching the age of 105—how to protect themselves against rape.

The older women are particularly taught how to break the noses of their assailants with just the palm of their hands, how to whack rapists in the groin using canes, and how to poke them in the eyes using just their fingers.

For those who are too weak to do these very physical self-defences, the program teaches them how to feign madness and other tricks to put fear into potential assailants.