Network Services

SMB: Server Message Block

Understanding SMB

SMB - Server Message Block Protocol - is a client-server communication protocol used for sharing access to files, printers, serial ports and other resources on a network. Servers make file systems and other resources (printers, named pipes, APIs) available to clients on the network.

The SMB protocol is known as a response-request protocol, meaning that it transmits multiple messages between the client and server to establish a connection. Clients connect to servers using TCP/IP, NetBEUI or IPX/SPX.

What runs SMB?

Microsoft Windows operating systems since Windows 95 have included client and server SMB protocol support. Samba, an open source server that supports the SMB protocol, was released for Unix systems.

Enumerating SMB

Lets check how many ports are open

We have 2 open ports

Lets run a detailed scan

SMB is running on ports 139 and 445

Lets use enum4linux to enumerate SMB

The name of the Workgroup is WORKGROUP

POLOSMB is the name of the machine and the OS version is 6.1

This share is interesting

Exploiting SMB

Lets use smbclient to connect to the share.

We are logged in.

Lets transfer the Information.txt file onto our machine and read it.

We can assume that this folder belongs to "John Cactus".

Reading the file, we can see that ssh has been enabled for employees to work from home, so we can also check out the .ssh folder on the smb share as it has ssh file that we can use to login to the machine using ssh.

Lets change directories into the .ssh folder and list the files.

To most useful file to us is the id_rsa file as we can use that to login through ssh.

Lets do this.

The username is cactus, lets login and read the file