How to disable NetBIOS port 137 (UDP) (2024)

FAQs

How to disable port 137 in NetBIOS? ›

Step 1: Open the Control Panel Step 2: Click on Windows Firewall/ Windows Defender firewall Step 3: Navigate to advanced settings. Step 4:Right click on inbound rules and click on new rule. Step 6:Select port and press next Step 7:Specify the port 137 under specific local ports, select UDP and press next.

Click Start, point to Settings, and then click Network Connections. Right-click the local area connection that you want to be statically configured, and then click Properties. Click Internet Protocol (TCP/IP) > Properties > Advanced, and then click the WINS tab. Click Disable NetBIOS over TCP/IP.

Disabling the use and support of NetBIOS can help to mitigate an attacker's ability to: poison and spoof responses, obtain a user's hashed credentials, inspect web traffic, etc. It's important to point out that NetBIOS itself is an API, not a networking protocol.

It is also recommended to disable NetBIOS over TCP/IP to improve network performance. Disabling NetBIOS over TCP/IP is especially recommended on Hyper-V and Windows Server cluster hosts with dedicated NICs used for traffic, such as iSCSI and Live Migration.

Right-click Local Area Connection, and then click Properties. Select Internet Protocol Version 4 (TCP/IPv4), click Properties, and then click Advanced. Click the WINS tab, and in the NETBIOS setting section, click Disable NETBIOS over TCP/IP. Click OK to close the properties windows.

Click on Start > Run > cmd. this means NetBIOS is enabled. Confirm that it's been disabled by going to Start > Run > cmd > nbstat -n.

NetBIOS provides three distinct services: Name service for name registration and resolution (ports: 137/udp and 137/tcp) Datagram distribution service for connectionless communication (port: 138/udp) Session service for connection-oriented communication (port: 139/tcp)

Step 1: Open the Control Panel Step 2: Click on Windows Firewall/ Windows Defender firewall Step 3: Navigate to advanced settings. Step 4:Right click on inbound rules and click on new rule. Step 6:Select port and press next Step 7:Specify the port 139 under specific local ports, select TCP and press next.

NetBIOS, an abbreviation for Network Basic Input/Output System, is a networking industry standard. It was created in 1983 by Sytek and is often used with the NetBIOS over TCP/IP protocol. However, it's also used in Token Ring networks, as well as by Microsoft Windows.

NetBIOS (Network Basic Input/Output System) is a network service that enables applications on different computers to communicate with each other across a local area network (LAN). It was developed in the 1980s for use on early, IBM-developed PC networks.

How do I change my NetBIOS settings? ›

The primary purpose of NetBIOS is to allow applications on separate computers to communicate and establish sessions to access shared resources, such as files and printers, and to find each other over a local area network (LAN).

In addition to turning off the NetBIOS service, you can prevent misuse of the NetBIOS service by closing TCP & UDP port 137 in your Windows firewall.

Why is it a risk? Using a command called NBSTAT (link below), an attacker can discover computer names, IP addresses, NetBIOS names, Windows Internet Name Service (WINS) names, session information and user IDs. This information can be used to mount focussed attacks on administrative accounts.

You can enable or disable network ports of switches that are part of your network. When you enable or disable a port, the administrative status of the port changes to UP or DOWN respectively. When you disable a port, the system marks that port as administratively down, without removing the port configurations.

Both your Active Directory domain FQDN and NetBIOS can be confirmed using simple command prompt commands. Type nbtstat -n and it will display some information. Under Name will be several entries: the NetBIOS will be one of the Group type.

The three standard ways of resolving NetBIOS names to IP addresses are through a local broadcast, using the local cache, or by using a NetBIOS name server. With a local broadcast, a broadcast is sent out on the network requesting the IP address of a specific host.

NetBIOS domain name: Typically, the NetBIOS domain name is the subdomain of the DNS domain name. For example, if the DNS domain name is contoso.com, the NetBIOS domain name is contoso. If the DNS domain name is corp.contoso.com, the NetBIOS domain name is corp.

What type of traffic is normally seen over UDP port 137? ›

UDP: Typically, NBNS uses UDP as its transport protocol. The well known UDP port for NBNS traffic is 137.

UDP uses IP to get a datagram from one computer to another. UDP works by gathering data in a UDP packet and adding its own header information to the packet. This data consists of the source and destination ports on which to communicate, the packet length and a checksum.

More information. NetBIOS over TCP traditionally uses the following ports: NBName: 137/UDP. NBName: 137/TCP.

Ports 80, 443, 8080 and 8443 (HTTP and HTTPS)

HTTP and HTTPS are the hottest protocols on the internet, so they're often targeted by attackers. They're especially vulnerable to cross-site scripting, SQL injections, cross-site request forgeries and DDoS attacks.

NetBIOS scan uses UDP port 137 to send and receive the NetBIOS data. If this port is blocked by your computer or in the remote network computers that you scan, the NetBIOS scan will not work. When you run NetBScanner in the first time, you might get a warning from the Firewall of Windows.

This means NetBIOS is now only used as a fallback in case mDNS and LLMNR queries fail. This means that devices will typically no longer use NetBIOS name resolution unless it is manually re-enabled, since mDNS responds first in most cases.

If you are on Windows-based network that is running NetBios, it is perfectly normal to have port 139 open in order to facilitate that protocol. If you are not on a network using NetBios, there is no reason to have that port open.

Today, DNS has replaced WINS, since Microsoft made changes to NetBIOS, allowing it to use the TCP/IP stack to perform its job (NetBIOS over TCP/IP) and most DNS servers are able to handle NetBIOS requests.

Do printers use NetBIOS? ›

NetBIOS over TCP/IP allows files and/or printers to be shared over the network.

The NBTSTAT Command

NetBT Statistics (Nbtstat.exe) is a command-line tool that can be used to view and troubleshoot network NetBIOS over TCP/IP (NetBT) name resolution.

137. tcp,udp. netbios-ns. NetBIOS is a protocol used for File and Print Sharing under all current versions of Windows.

Common UDP ports are 53 (DNS), 88 (Kerberos), 137/138/445 (Windows), and 161 (SNMP). When investigating a DDoS attack, look for UDP traffic with high numbered network ports (1024+).

SMB is a network file sharing protocol that requires an open port on a computer or server to communicate with other systems. SMB ports are generally port numbers 139 and 445.

Firewall protection:

A proper firewall ensures that ports are not open for vulnerable attacks by Cybercriminals.

Is a port open if it is listening? ›

The listening port listens to applications or processes on the network port. It is acting just like the communication endpoint. Using the firewall, we can open or closed each listening port. The open port can be defined as a network port used to accept incoming packets from remote locations.

When a port is in error-disabled state, it is effectively shut down and no traffic is sent or received on that port. The port LED is set to the orange color and, when you issue the show interfaces command, the port status shows as Errdisabled.

Use the switchport port-security command to enable port security.

Enter "telnet + IP address or hostname + port number" (e.g., telnet www.example.com 1723 or telnet 10.17. xxx. xxx 5000) to run the telnet command in Command Prompt and test the TCP port status. If the port is open, only a cursor will show.

NetBIOS provides three distinct services: Name service for name registration and resolution (ports: 137/udp and 137/tcp) Datagram distribution service for connectionless communication (port: 138/udp) Session service for connection-oriented communication (port: 139/tcp)

NetBIOS (Network Basic Input/Output System) is a network service that enables applications on different computers to communicate with each other across a local area network (LAN). It was developed in the 1980s for use on early, IBM-developed PC networks.