Bitmessage is a P2P communications protocol used to send encrypted messages to another person or to many subscribers. It is decentralized and trustless, meaning that you need-not inherently trust any entities like root certificate authorities. It uses strong authentication which means that the sender of a message cannot be spoofed, and it aims to hide “non-content” data, like the sender and receiver of messages, from passive eavesdroppers like those running warrantless wiretapping programs. (bitmessage.org)
The Shadow Brokers published in his first post on Steemit a Bitmessage address to contact them:
BM-NBvAHfp5Y6wBykgbirVLndZtEFCYGht8