Sever Message Block

A server message block (“SMB,” not to be confused with “small and medium businesses,” another common abbreviation) is an application layer network file-sharing protocol which allows systems within the same network to share and access files and resources easily. SMBs facilitate network communication between client applications and the server. 

SMB was originally developed for Windows OS but a later software implementation called Samba made it possible for SMB to be used on Mac OSs or UNIX.

Server message blocks run on top of TCP/IP, via NetBIOS/NetBEUI, or over other network protocols, letting the application access files, read/write/create/update files, or request other resources or services from a remote server.

The original protocol, SMB 1.0. was introduced in the early 1990s by Barry Feigenbaum. SMB3.1.1, the latest version, was introduced with Windows 10 and Windows Server 2016. Version 3.1.1 supports AES encryption and implements pre-authentication integrity checks using SHA-512 hash. Since Windows 95, all Windows OSs include SMB protocol support.

An open source version called the Common Internet File System (CIFS) is available through the Internet Engineering task Force (IETF).

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