It took US$100,000 plus expenses, and the opportunity for a reduced prison sentence, for the smartphone developer to collaborate with the Federal Bureau of Investigation (FBI) in 2018 and kick-start Operation Trojan Shield, according to a court document.

Three years later, the investigation involving 9,000 law enforcement officers from 17 countries saw authorities monitor 27 million messages from 12,000 devices in 100 countries and track the activities of more than 300 organised crime groups, the European Union's law enforcement agency, Europol, said in a statement.