/ˌɛs-ɛm-ˈbiː/
n. “Talk to your neighbor’s files like they’re your own.”
SMB, short for Server Message Block, is a network protocol that enables shared access to files, printers, and other resources between computers. Originally developed by IBM and later popularized by Microsoft, SMB allows a client machine to communicate with a server to read, write, and manage files over a network as if they were local.
The protocol works at the application layer and relies on transport protocols such as TCP for reliable delivery. SMB is widely used in enterprise and home networks, powering Windows file sharing, integration with NAS devices, and even interactions between non-Windows systems through implementations like Samba.
Modern versions, such as SMB 2 and SMB 3, introduced performance improvements, stronger security, and additional features like encryption, improved caching, and resilient handles for network interruptions. SMB 3, for example, can encrypt data in transit, reducing the risk of eavesdropping on sensitive files.
In practical terms, SMB allows a user on one computer to open documents, copy files, or print to a remote printer as if it were directly attached. Administrators can manage permissions, control access, and ensure file consistency across multiple devices. SMB is particularly crucial in shared work environments where collaboration requires seamless access to common directories and resources.
For example, a small office using a NAS can rely on SMB to serve shared project files to all employees, while ensuring only authorized personnel can edit or delete documents. Similarly, network printers can be accessed via SMB without needing specialized drivers on each client.
SMB has also become a target for attackers. Because it exposes shared resources over the network, vulnerabilities in SMB implementations have been exploited for ransomware and other attacks, highlighting the importance of updates, proper access controls, and firewalls.
Alternatives like NFS exist for UNIX/Linux environments, but SMB remains the standard for Windows networks and cross-platform file sharing. In essence, SMB provides the language that computers use to negotiate shared resources efficiently, securely, and transparently across a network.