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Networking Fundamentals · Foundational

Server Message Block (SMB)

The Windows file and printer sharing protocol, running directly over TCP port 445.

Definition

SMB (CIFS for the older dialect) provides access to shared folders and printers. SMBv1 is insecure and was exploited by WannaCry, so SMB 3.x with encryption is recommended. Older NetBIOS-based SMB used ports 137-139.

Example

net use Z: \\fileserver\share maps a drive over SMB on port 445.

Exam tip

SMB = TCP 445; block it at the Internet edge and disable SMBv1.

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