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**NetBIOS** stands for _Network Basic Input Output System_. It is a software protocol that allows applications, PCs, and Desktops on a local area network (LAN) to communicate with network hardware and to transmit data across the network. Software applications that run on a NetBIOS network locate and identify each other via their NetBIOS names. A NetBIOS name is up to 16 characters long and usually, separate from the computer name. Two applications start a NetBIOS session when one (the client) sends a command to “call” another client (the server) over **TCP Port 139**. (extracted from [here](https://www.thewindowsclub.com/smb-port-what-is-port-445-port-139-used-for))
While Port 139 is known technically as ‘NBT over IP’, Port 445 is ‘SMB over IP’. **SMB** stands for ‘**Server Message Blocks**’. Server Message Block in modern language is also known as **Common Internet File System**. The system operates as an application-layer network protocol primarily used for offering shared access to files, printers, serial ports, and other sorts of communications between nodes on a network.
For instance, on Windows, SMB can run directly over TCP/IP without the need for NetBIOS over TCP/IP. This will use, as you point out, port 445. On other systems, you’ll find services and applications using port 139. This means that SMB is running with NetBIOS over TCP/IP\*\*.\*\* (extracted from [here](https://www.thewindowsclub.com/smb-port-what-is-port-445-port-139-used-for))
Server Message Block (`SMB`) is a **client-server** protocol that regulates **access to files** and entire directories and other network resources such as printers, routers, or interfaces released for the network. The main application area of the protocol has been the **Windows** operating system series in particular, whose network services support SMB in a downward-compatible manner - which means that devices with newer editions can easily communicate with devices that have an older Microsoft operating system installed.\
With the free software project **Samba**, there is also a solution that enables the use of **SMB in Linux** and Unix distributions and thus cross-platform communication via SMB.
An SMB server can provide **arbitrary parts of its local file system as shares**. Therefore the **hierarchy visible** to a client is partially **independent** of the **structure** on the **server**. **Access rights** are defined by `Access Control Lists` (`ACL`). They can be controlled in a **fine-grained manner** based on attributes such as **`execute`**, **`read`**, and **`full access`** for individual users or user groups. The **ACLs** are defined **based on the shares** and therefore do not correspond to the rights assigned locally on the server.
From book _**Network Security Assessment 3rd edition**_
With an anonymous null session you can access the IPC$ share and interact with services exposed via named pipes. The enum4linux utility within Kali Linux is particularly useful; with it, you can obtain the following:
If you don't know what is NTLM or you want to know how it works and how to abuse it, you will find very interesting this page about **NTLM** where is explained **how this protocol works and how you can take advantage of it:**
To look for possible exploits to the SMB version it important to know which version is being used. If this information does not appear in other used tools, you can:
It may be possible that you are restricted to display any shares of the host machine and when you try to list them it appears as if there aren't any shares to connect to. Thus it might be worth a short to try to manually connect to a share. To enumerate the shares manually you might want to look for responses like NT\_STATUS\_ACCESS\_DENIED and NT\_STATUS\_BAD\_NETWORK\_NAME, when using a valid session (e.g. null session or valid credentials). These may indicate whether the share exists and you do not have access to it or the share does not exist at all.
Specially interesting from shares are the files called **`Registry.xml`** as they **may contain passwords** for users configured with **autologon** via Group Policy. Or **`web.config`** files as they contains credentials.
{% hint style="info" %}
The **SYSVOL share** is **readable** by all authenticated users in the domain. In there you may **find** many different batch, VBScript, and PowerShell **scripts**.\
You should **check** the **scripts** inside of it as you might **find** sensitive info such as **passwords**.
crackmapexec can execute commands **abusing** any of **mmcexec, smbexec, atexec, wmiexec** being **wmiexec** the **default** method. You can indicate which option you prefer to use with the parameter `--exec-method`:
Both options will **create a new service** (using _\pipe\svcctl_ via SMB) in the victim machine and use it to **execute something** (**psexec** will **upload** an executable file to ADMIN$ share and **smbexec** will point to **cmd.exe/powershell.exe** and put in the arguments the payload --**file-less technique-**-).\
This attack uses the Responder toolkit to **capture SMB authentication sessions** on an internal network, and **relays** them to a **target machine**. If the authentication **session is successful**, it will automatically drop you into a **system****shell**.\
[**More information about this attack here.**](../generic-methodologies-and-resources/pentesting-network/spoofing-llmnr-nbt-ns-mdns-dns-and-wpad-and-relay-attacks.md)
The Windows library URLMon.dll automatically try to authenticaticate to the host when a page tries to access some contect via SMB, for example: `img src="\\10.10.10.10\path\image.jpg"`
Similar to SMB Trapping, planting malicious files onto a target system (via SMB, for example) can illicit an SMB authentication attempt, allowing the NetNTLMv2 hash to be intercepted with a tool such as Responder. The hash can then be cracked offline or used in an [SMB relay attack](pentesting-smb.md#smb-relay-attack).
While Port 139 is known technically as ‘NBT over IP’, Port 445 is ‘SMB over IP’. SMB stands for ‘Server Message Blocks’. Server Message Block in modern language is also known as Common Internet File System. The system operates as an application-layer network protocol primarily used for offering shared access to files, printers, serial ports, and other sorts of communications between nodes on a network.
#These are the commands I run in order every time I see an open SMB port
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