WASHINGTON — The world's police forces recently arrested hundreds of suspects across the globe after three years of listening in on an app that was supposed to be the most securely encrypted app in the world.

The huge surveillance operation started years ago, when a convicted drug smuggler offered the back door of his special new gangster phone to the FBI. Here are the details:

Reuters reports that the ANoM app saga started in mid-2018, when a convicted smuggler met with FBI agents and made them an offer.

In exchange for a possible reduction in his sentence, he would give the bureau a back door into the encrypted communications of a vast network of international organised crime groups.

The smuggler had invested in developing an encrypted device which could be used by criminals around the world to avoid police surveillance.

The new device, called ANoM, was a modified mobile phone, fitted with customised encryption software that made it very secure.

The smuggler planned to provide ANoM phones to a network of distributors linked to organised crime groups.

A new user would need to be vouched for by an existing user, which gave the system an added level of trust.

Within three years, ANoM would be used by criminals in 90 countries to send tens of millions of messages, referring to murder plots, drug deals, corruption, and money laundering, including 450,000 images of big bundles of cash and cocaine. And all along the FBI and other police forces were listening in.

The details of the operation, codenamed Trojan Shield, were included in an FBI affidavit filed in a US court on 17 May 2021.

The affidavit states that more than 20,000 encrypted devices had been used by 300 criminals in more than 100 countries. 27 million messages had been reviewed by police services over a period of 18 months, and at least 800 arrests were made while 700 locations were searched worldwide.