NETBIOS Session Service
NETBIOS-SSN (NetBIOS Session Service) is used for network communication, primarily for file and printer sharing over a local network. It operates on port 139 and allows applications on different computers to communicate within a local network. This service is essential for older Windows networks and systems that rely on NetBIOS for resource sharing.
What is NETBIOS Session Service
NETBIOS-SSN, or NetBIOS Session Service, is a protocol that operates on port 139 and is used for network communication, particularly for file and printer sharing within a local network. It is part of the NetBIOS (Network Basic Input/Output System) suite, which provides services related to the session layer of the OSI model, allowing applications on different computers to communicate over a local network.
Historically, NetBIOS was developed in the early 1980s by IBM for their PC Network. It was later adopted by Microsoft for their early networking products, including LAN Manager and Windows for Workgroups. Despite the advent of more modern protocols, NetBIOS remains in use, especially in legacy systems and networks that have not transitioned to newer technologies.
NETBIOS-SSN is crucial for older Windows networks and systems that rely on NetBIOS for resource sharing. It enables the establishment of sessions between computers, facilitating the sharing of files and printers. However, its use has declined with the rise of more secure and efficient protocols like SMB (Server Message Block) over TCP/IP.
While NETBIOS-SSN is still supported in modern Windows operating systems, it is often disabled by default due to security concerns. Organizations are encouraged to transition to more secure protocols to mitigate the risks associated with using NetBIOS.
NETBIOS Session Service runs on TCP and UDP port 139 and is official IANA port.Security risk
Leaving port 139 open can expose a network to various security risks, including unauthorized access and data breaches. Attackers can exploit vulnerabilities in the NetBIOS protocol to gain access to sensitive information or disrupt network services. It is recommended to disable NetBIOS over TCP/IP if it is not needed and to use more secure protocols for network communication.
In our UFW tutorial you can follow instructions how you can configure UFW to close port 139. Use StackChanges to monitor if the NETBIOS Session Service port is closed and stays closed. StackChanges will send an alert if port 139 is open again.