In a press release last week, the International Committee of the Red Cross (ICRC) said they have only been able to carry out two prison visits to the central prisons in Damascus and Aleppo since 2011.

"That was good, but it is not enough. Of course, some places of detention are in areas too dangerous for us to enter. But this limited access means that there is no monitoring of the situation of detainees. That would be very worrying in any armed conflict and it is certainly a serious concern in Syria," the ICRC said.

But it is not only the regime that is holding detainees. Rebel fighters in opposition controlled areas have captured their own detainees too. With limited access amid a state of war, it is not clear how many people are detained by the Free Syrian Army and other rebel factions.

Zaidoun and Keffah know far too well the risks associated with speaking out, but they say fear of detention will not stop them.

"Of course I am afraid, but freedom tastes so good. No one, other than those who taste it for the first time, know what that is like. We have started a journey from which there is no turning back," Zaidoun said. "It will be a betrayal for those who lost their lives."

Keffah, whose name means struggle in Arabic, believes she has a duty to the next generation of Syrians.

"I don't want to take anything from this. I want the day to come when another generation has a better life than the one we had," she said.

"To me, my father, his generation and the one before his are all criminals because they were silent. Imagine us staying silent and leaving this for our children."