But now some of the rebels fighting Assad say they have set up a mukhabarat of their own to "protect the revolution", monitor sensitive military sites and gather military information to help rebels plan attacks against government forces.
"We formally formed the unit in November. It provides all kind of information to (opposition) politicians and fighters. We are independent and just serve the revolution," said a rebel intelligence officer who goes under the name Haji.
Rebel commanders had put Reuters in touch with Haji, who is based in Syria, via Skype on condition he not be identified.
Haji said most of the rebel mukhabarat's members were army defectors and former intelligence officers, and that the information they gathered was distributed to all anti-Assad factions and rebel brigades without discrimination.
However, the organisation appears to operate independently from the main opposition Syrian National Coalition and the Free Syrian Army, effectively answering to itself.
Haji was careful to distinguish between its methods and those of the secret police under Assad. "Our work is organised, we have an internal law and we are committed to international laws and human rights," he said.