According to Operational Taskforce (OTF) GRIMM, the Europol group set up to tackle the problem, the teenage hitmen are recruited on social media, and are given their instructions in a "gamified" way, imitating how computer games work.
Andy Kraag, the head of Europol's European Serious and Organised Crime Centre, calls it the "calculated outsourcing of murder" to vulnerable young people.
OTF GRIMM currently involves 11 countries affected by the VaaS phenomenon - Belgium, Denmark, Finland, France, Germany, Iceland, the Netherlands, Norway, Spain, Sweden, and the United Kingdom.
Swedish Police
The leader of the Foxtrot Network, Rawa Majid, has fled Sweden and his later operating base in Turkey, and is now based in the Iranian capital Tehran. Police believe some of the VaaS attacks have been carried out for the Iranian regime, including a hand grenade attack on the Israeli embassy in Copenhagen, though other attacks are part of Foxtrot's drugs turf wars.
Diamant Salihu, an investigative journalist for the Swedish broadcaster SVT, has been researching Foxtrot and its Iranian links for three years.
"The regime is ordering the leader of the Foxtrot Network to instigate his network to commit attacks against the Iranian regime's enemies," he said.
"It can be dissidents, journalists that are in the opposition against the regime, and it can also be Israeli targets."