What is NetBIOS? How to use it in penetration testing? Here is all you need to know about NetBIOS as penetration tester.

NetBIOS.md

NetBIOS (Network Basic Input/Output System) is a legacy protocol that still plays a role in many Windows networks. It handles several functions:

• Name Servicing:
  NetBIOS allows computers to register and resolve 16-character names. This makes it possible to identify and communicate with devices on a local network using human-readable names.

• Connectionless Communication:
  It supports communication methods that don’t require a sustained connection. This means messages can be sent without establishing a persistent link.

• Session Layer Functions:
  While primarily associated with lower-level operations, NetBIOS also provides some session layer capabilities to manage communication sessions.

Additionally, Windows networks use a Browser Service based on NetBIOS. This service maintains a list of all machines within the domain or TCP/IP network segment, which can then be browsed by users in the “Network Neighborhood” or “My Network Places.”

NetBIOS Names

• A NetBIOS name is a 16-character ASCII string that uniquely identifies a device on a network.
• This name allows systems to be recognized by human-friendly identifiers rather than just IP addresses.

Using nbtstat on Windows

The nbtstat command is a useful tool for enumerating NetBIOS information:

• nbtstat (no options):
  Displays your own machine’s NetBIOS information, including the registered names and their status.
  Example:

  nbtstat

• nbtstat -n:
  Shows the local NetBIOS name table. This table lists all the names your machine has registered (both unique and group names).
  Example:

  nbtstat -n

• nbtstat -A IPADDRESS:
  Retrieves the NetBIOS table for a remote computer by using its IP address. This is helpful for identifying what NetBIOS names a remote host is using.
  Example:

  nbtstat -A 192.168.1.10

• nbtstat -c:
  Displays the contents of the local NetBIOS name cache. This cache holds recently resolved NetBIOS names from the network.
  Example:

  nbtstat -c

Practical Implications

• Enumeration:
  Network administrators and even penetration testers can use these commands to gather information about active devices, their roles, and shared resources on the network.

• Security Considerations:
  Because NetBIOS can reveal sensitive information like shared resources and network structure, it can be exploited by attackers to map out the network and plan further attacks.