SBBS (Secure Bulletin Board System) is an encrypted messaging protocol used to secure communication between Beam wallets. Initially, this protocol only allowed for the interactive creation of Mimblewimble transactions. Eventually, SBBS was adapted to fit many different scenarios of passing information between wallets, such as Atomic Swap marketplace, price feed metadata, and more.
SBBS is a subsystem within each Beam node designed to leak no metadata that can aid in the deanonymization of Beam users. See SBBS Design and Beam News Channels for additional information regarding SBBS.