SMB (Server Message Block) and SMB2 are Windows file-sharing protocols used to access shared folders, printers, and other network resources. In Microsoft environments, they also carry Distributed File System (DFS) referral traffic, which is the mechanism that points a client to the correct file server. That makes SMB/SMB2 a core part of routine internal network communication, not just simple file access.
These protocols matter in cyber security because they move trusted east-west traffic that can be abused if parsing is flawed or if attackers can reach internal services. A malformed SMB or SMB2 message, including a crafted DFS referral response, may trigger crashes, service disruption, or other failures in vulnerable systems. Defenders watch SMB/SMB2 activity to inventory file-sharing paths, detect unusual referral behavior, validate patching, and investigate outages on Windows servers that depend on shared storage and namespace resolution.