Three people were arrested on Tuesday after Dutch and French police smashed a sophisticated encryption service used by criminal gangs across Europe.
Detectives from a joint investigation team have been reading messages sent on the Matrix chat service since September.
They closed it down during an operation involving Lithuanian and Spanish police.
"The founders were convinced that the service was superior and more secure than previous applications used by criminals," said a statement from the European Union Agency for Criminal Justice Cooperation (Eurojust).
Matrix breakthrough
The breakthrough, three years after police cracked the Encrochat and SkyECC networks, enabled them to read millions of messages between suspected criminals.
"The infrastructure of the Matrix platform was technically more complex than previous platforms," Eurojust said.
Using more than 40 servers in several countries, the most important MATRIX servers were tracked down in France and Germany.
"It is not the first time and will not be the last time that authorities are able to read criminals' messages in real time," Eurojust said.
Journalist murdered
Dutch media reported that new encryption tool was discovered following the murder in July 2021 of Peter R. de Vries who was the country's best-known crime reporter.
Police found the software on a Google Pixel phone in the getaway car of the man who shot him, the NOS public broadcaster said.
During an investigation into the messaging service, police discovered users were only able to join via invitation. They eventually intercepted and deciphered more than 2.3 million messages in 33 languages linked to crimes such as international drug trafficking, arms trafficking and money laundering.
In 2016, Michael Rogers, the director of America's National Security Agency warned of the dangers of encryption after it emerged that the men behind the November 2015 massacre on the streets of Paris had been using the system which prevented intelligence officials from picking up the trail.
"As a result, we did not generate the insights ahead of time," he told Yahoo News. "Clearly, had we known, Paris would not have happened."
(With newswires)
