SMB - cysec-all-in-one(A.R)

SMB Cheat Sheet

Overview

SMB (Server Message Block) is a network file sharing protocol used for providing shared access to files, printers, and serial ports. It operates at the Application Layer (Layer 7) of the OSI model.

Common Uses

Accessing files and networks shares on remote servers.
Printing to shared printers on the network.
Interprocess communication between programs on the same server.

Common SMB Message Types

SMB Message Type	Description	Purpose
SMB_COM_READ	Request to read a file from the server.	Used to retrieve the contents of a file.
SMB_COM_WRITE	Request to write data to a file on the server.	Used to modify an existing file or create a new one.
SMB_COM_CREATE	Request to create a new file or directory.	Used for creating new resources in shared folders.
SMB_COM_DELETE	Request to delete a file or directory.	Used to remove files or folders from the server.
SMB_COM_TRANSACTION	Perform a transaction over the SMB session.	Used for complex operations that require multiple steps.

SMB Packet Structure

Field	Size (bytes)	Description
Protocol ID	2	Always set to 0xFF534D42 (‘SMB’)
Command	1	Indicates the type of SMB command being issued
Error Code	2	Error code indicating the result of the SMB command
Flags	2	Flags indicating various options (e.g., case sensitivity)
PID High	2	High word of the process ID
UID	2	User ID assigned when a connection is established
MID	2	Multiplexer ID for tracking requests
Word Count	1	Number of words in the parameter block
Parameter Block	Variable	Parameters specific to the command being requested
Data Block	Variable	Contains the data associated with the request (file contents, etc.)

Common SMB Ports

Port	Description
445	Direct SMB over TCP without NetBIOS encapsulation.
139	SMB over NetBIOS, commonly used for legacy systems.

Security Considerations

SMB Signing: Provides integrity and authenticity for SMB communications.
SMB Encryption: Protects data in transit to prevent eavesdropping and tampering.
Guest Access: Should be disabled to prevent unauthorized access to shared resources.

Common Commands for SMB Scanning and Enumeration

Command	Description
`nmap -p 445 --script=smb-os-discovery <target>`	Discover the operating system on a target SMB server.
`nbtscan -r <target>`	Scans for NetBIOS services and shares on target IPs.
`enum4linux -a <target>`	Enumerates SMB shares, users, and groups from a target.

This cheat sheet provides a quick reference for understanding and utilizing the SMB protocol, including its structure, common commands, and security considerations.