The SMB protocol enables “inter-process communication,” which is the protocol that allows applications and services on networked computers to talk to each other. SMB enables the core set of network services such as file, print, and device sharing.

History

In early versions of Windows, SMB ran on top of the NetBIOS network architecture. Microsoft changed SMB in Windows 2000 to operate on top of TCP and use a dedicated IP port. Current versions of Windows continue to use that same port.

SMB Protocol Dialects

Just like any language, computer programmers have created different SMB dialects use for different purposes. For example, Common Internet File System (CIFS) is a specific implementation of SMB that enables file sharing. Many people mistake CIFS as a different protocol than SMB, when in fact they use the same basic architecture.

Important SMB implementations include:

• CIFS: CIFS is a common file sharing protocol used by Windows servers and compatible NAS - devices.
• Samba: Samba is an open-source implementation of Microsoft Active Directory that allows non-Windows machines to communicate with a Windows network.
• Tuxera SMB: Tuxera is also a proprietary SMB implementation that runs in either kernel or user-space.
• Likewise: Likewise is a multi-protocol, identity aware network file sharing protocol that was purchased by EMC in 2012.

What Are Ports 139 And 445?

SMB has always been a network file sharing protocol. As such, SMB requires network ports on a computer or server to enable communication to other systems. SMB uses either IP port 139 or 445.

• Port 139: SMB originally ran on top of NetBIOS using port 139. NetBIOS is an older transport layer that allows Windows computers to talk to each other on the same network.
• Port 445: Later versions of SMB (after Windows 2000) began to use port 445 on top of a TCP stack. Using TCP allows SMB to work over the internet.

Overview of Server Message Block signing

SMB signing (also known as security signatures) is a security mechanism in the SMB protocol. SMB signing means that every SMB message contains a signature that is generated by using the session key. The client puts a hash of the entire message into the signature field of the SMB header.

History

• SMB 1.0 signing first appeared in Microsoft Windows 2000, Microsoft Windows NT 4.0, and Microsoft Windows 98 using MD5.
• SMB 2.02 signing was improved by the introduction of hash-based message authentication code (HMAC) SHA-256.