The FBI and the Australian Federal Police created a fake end-to-end encrypted chat platform designed solely to catch criminals. Law enforcement was able to arrest 800 people and seize 8 tons of cocaine, 22 tons of cannabis and cannabis resin, 2 tons of synthetic drugs (amphetamine and methamphetamine) Law enforcement also seized 250 firearms, 55 luxury vehicles and over $48 million in worldwide currencies and cryptocurrencies. The FBI, AFP, and the CHS built a master key into the encryption system which surreptitiously attaches to each message and enables law enforcement to decrypt and store the message as it is transmitted.
Source: https://www.bleepingcomputer.com/news/security/fbi-and-afp-created-a-fake-encrypted-chat-platform-to-catch-criminals/