https://www.vice.com/en_us/article/v7veg8/anom-app-source-code-operation-trojan-shield-an0m

The FBI operation in which the agency intercepted messages from thousands of encrypted phones around the world was powered by cobbled together code. Motherboard has obtained that code and is now publishing sections of it that show how the FBI was able to create its honeypot. The code shows that the messages were secretly duplicated and sent to a “ghost” contact that was hidden from the users’ contact lists. This ghost user, in a way, was the FBI and its law enforcement partners, reading over the shoulder of organized criminals as they talked to each other.

Last year, the FBI and its international partners announced Operation Trojan Shield, in which the FBI secretly ran an encrypted phone company called Anom for years and used it to hoover up tens of millions of messages from Anom users. Anom was marketed to criminals, and ended up in the hands of over 300 criminal syndicates worldwide. The landmark operation has led to more than 1,000 arrests including alleged top tier drug traffickers and massive seizures of weapons, cash, narcotics, and luxury cars.