Research has found that terrorist groups like Isis are using slaves to increase funding by attracting rapists and abusers to their organisations.
The Henry Jackson Society thinktank claims this is commonplace in groups working in the Middle East and Africa, according to The Independent.
It is thought kidnapping allowed Isis to gain between £7.6 million and £22.8 million last year and some suggest the group will make even more this year, to offset a drop in profits from other industries in their territories.
Author of the report Nikita Malik says whilst human traffickers and terrorists are usually treated as separate groups, they are working together in some cases.
She said: "As the [terror] groups begin to lose territory, they are gaining strongholds on trafficking routes that are being exploited.”
Isis previously told the world that it was abducting both women and girls to be used as sex slaves in the genocide agaist the Yazidis of Sinjar.
The Henry Jackson Society said this “served as an incentive for new recruits and foreign fighters, with the promise of wives and sex slaves acting as a ‘pull factor’.”
Boko Haram has also used both rape and forced marriages to increase the amount of children in territories they own, so it can teach them jihadi ideology.
It is also suggested that terrorists are also trafficking drugs and firearms as well as being a part of money laundering. In order to do this groups often target former gang members for recruitment for their knowledge.
Major hotspots for this include Niger and Nigeria in Africa, as well as Isis's Middle-Eastern territories such as Syria, Libya and Iraq.