07-NetBIOS (137,138,139)

Intro:

(Network Basic Input/Output System)

NetBIOS is an API and a set of network protocols for providing communication services over a local network. it's used primarily to allow applications on different computers to find and interact with each other on a network.

NetBIOS with SMB:

**Functions: **

• Name Service (NetBIOS-NS): Allows computers to register, unregister and resolve names in a local network. Port:UPD137
• Datagram Service (NetBIOS-DGM): Supports connectionless communication and broadcasting. Port:UDP138
• Session Service(NetBIOS-SSN): Supports connection-oriented communication for more reliable data transfers. Port:TCP139

While NetBIOS and SMB were once closely linked, modern networks rely primarily on SMB for file and printer sharing, often using DNS and other mechanisms for name resolution instead of NetBIOS.

Modern implementation of Windows primarily use SMB and can work without NetBIOS, however, NetBIOS over TCP139 is required for backward compatibility and are often enabled together.

NetBIOS Tools:

1. NBTScan

• it scans networks for NetBIOS name information.

  ntbscan <ip_subnet>

2. nmblookup

• Check help menu