There are more details in a recently unsealed search warrant against a GMail user:
https://storage.courtlistener.com/recap/gov.uscourts.casd.70...An informant (confidential human source, or "CHS") helped the FBI and AFP (Australian Federal Police) develop and distribute Anom to criminal gangs (transnational criminal organizations, or "TCOs"):
> The CHS offered this next generation device, named “Anom,” to the FBI to use in ongoing and new investigations. The CHS also agreed to offer to distribute Anom devices to some of the CHS’s existing network of distributors of encrypted communications devices, all of whom have direct links to TCOs.
Anom was specifically designed from the ground up with an encryption backdoor:
> Before the device could be put to use, however, the FBI, AFP, and the CHS built a master key into the existing encryption system which surreptitiously attaches to each message and enables law enforcement to decrypt and store the message as it is transmitted. A user of Anom is unaware of this capability. By design, as part of the Trojan Shield investigation, for devices located outside of the United States, an encrypted “BCC” of the message is routed to an “iBot” server located outside of the United States, where it is decrypted from the CHS’s encryption code and then immediately re-encrypted with FBI encryption code. The newly encrypted message then passes to a second FBI-owned iBot server, where it is decrypted and its content available for viewing in the first instance.
Naturally, the FBI can't spy on domestic communications without a warrant, so they got the AFP to do it for them:
> FBI geo-fenced the U.S., meaning that any outgoing messages from a device with a U.S. MCC would not have any communications on the FBI iBot server. But if any devices landed in the United States, the AFP agreed to monitor these devices for any threats to life based on their normal policies and procedures.
Closing Sky Global and Encrochat drove criminals to Anom:
> Since March 12, 2021, as a direct result of the Sky Global charges, there are now close to 9000 active Anom users. The criminals who use hardened encrypted devices are constantly searching for the next secure device, and the distributors of these devices have enabled criminals’ impenetrable communications on these devices for years.
Finally, the FBI quite directly admits their goal is to shake confidence in encrypted messaging:
> A goal of the Trojan Shield investigation is to shake the confidence in this entire industry because the FBI is willing and able to enter this space and monitor messages.
There's also a number of sample conversations in the warrant application showing criminals openly talking about moving drugs and other illegal activities with absolutely no code. Definitely worth a read.