Port 137 (tcp/udp) (2024)

Port 137 (tcp/udp) (3) Home » Ports Database » Port Details

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Port(s)ProtocolServiceDetailsSource
137 tcp,udp netbios-ns NetBIOS is a protocol used for File and Print Sharing under all current versions of Windows. While this in itself is not a problem, the way that the protocol is implemented can be.

NetBios services:
NETBIOS Name Service (TCP/UDP: 137)
NETBIOS Datagram Service (TCP/UDP: 138)
NETBIOS Session Service (TCP/UDP: 139)

By default, when File and Print Sharing is enabled it binds to everything, including TCP/IP (The Internet Protocol), rather than just the local network, meaning your shared resources are available over the entire Internet for reading and deletion, unless configured properly. Any machine with NetBIOS enabled and not configured properly should be considered at risk. The best protection is to turn off File and Print Sharing, or block ports 135-139 completely. If you must enable it, use the following guidelines:

1. Use strong passwords, containing non-alphanumeric characters.
2. Attach "$" at the end of your share names (the casual snooper using net view might not see them).
3. Unbind File and Print Sharing from TCP/IP and use NetBEUI instead (it's a non-routable protocol).
4. Block ports 135-139 in your router/firewall.

Keep in mind that you might still be leaking out information about your system that can be used against you (such as your computer and workgroup names) to the entire Internet, unless ports are filtered by a firewall.

There is also a Critical Windows RPC vulnerability affecting ports 135,139 and 445, as detailed here: MS Technet Security Bulletin [MS03-026]

The following trojans/backdoors also use these ports: Chode, God Message worm, Msinit, Netlog, Network, Qaz
W32.HLLW.Moega [Symantec-2003-080813-3234-99] (2003.08.08) - worm with backdoor capabilities, opens TCP ports 139 and 445.
W32.Crowt.A@mm [Symantec-2005-012310-2158-99] (2005.01.23) - mass mailing worm, opens a backdoor, logs keystrokes. Uses ports 80 and 137.
W32.Reidana.A [Symantec-2005-032515-4042-99] (2005.03.27) - worm that spreads using the MS DCOM RPC vulnerability (MS Security Bulletin [MS03-026]) on port 139. The worm attempts to download and execute a remote file via FTP. Opens TCP port 4444.

Windows Internet Naming Service (WINS) also uses this port (UDP).

Sygate Personal Firewall comes with a default rule set that blocks all udp requests, however if udp requests originates from source port 137 or 138 they are allowed, thus a malicious person could get access to all open udp ports on a target merely by sending all requests from source port 137 or 138.
References: [SECUNIA-7930]

SG
137 tcp,udp NetBIOS NetBIOS Name Service (official) Wikipedia
137 tcp trojan Chode, Nimda Trojans
137 udp trojan Bugbear, Msinit, Opaserv, Qaz Trojans
137 tcp Chode [trojan] Chode Neophasis
137 tcp Qaz [trojan] Qaz Neophasis
137 udp Msinit [trojan] Msinit Neophasis
137 udp threat Femot Bekkoame
137 udp threat Msinit Bekkoame
137 tcp threat Chode Bekkoame
137 tcp,udp netbios-ns NETBIOS Name Service IANA
11 records found

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Port 137 (tcp/udp) (4)Port 137 (tcp/udp) (5)

Related ports: 135 138 139 445

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External Resources
SANS Internet Storm Center: port 137

Notes:
Port numbers in computer networking represent communication endpoints. Ports are unsigned 16-bit integers (0-65535) that identify a specific process, or network service. IANA is responsible for internet protocol resources, including the registration of commonly used port numbers for well-known internet services.
Well Known Ports: 0 through 1023.
Registered Ports: 1024 through 49151.
Dynamic/Private : 49152 through 65535.

TCP ports use the Transmission Control Protocol, the most commonly used protocol on the Internet and any TCP/IP network. TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and that packets will be delivered in the same order in which they were sent. Guaranteed communication/delivery is the key difference between TCP and UDP.

UDP ports use the Datagram Protocol. Like TCP, UDP is used in combination with IP (the Internet Protocol) and facilitates the transmission of datagrams from one computer to applications on another computer, but unlike TCP, UDP is connectionless and does not guarantee reliable communication; it's up to the application that received the message to process any errors and verify correct delivery. UDP is often used with time-sensitive applications, such as audio/video streaming and realtime gaming, where dropping some packets is preferable to waiting for delayed data.

When troubleshooting unknown open ports, it is useful to find exactly what services/processes are listening to them. This can be accomplished in both Windows command prompt and Linux variants using the "netstat -aon" command. We also recommend runnig multiple anti-virus/anti-malware scans to rule out the possibility of active malicious software. For more detailed and personalized help please use our forums.

Please use the "Add Comment" button below to provide additional information or comments about port 137.

User Reviews/Comments:

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avg: Port 137 (tcp/udp) (6)Port 137 (tcp/udp) (7)Port 137 (tcp/udp) (8)Port 137 (tcp/udp) (9)Port 137 (tcp/udp) (10)

by anonymous Port 137 (tcp/udp) (12) - 2023-06-22 11:37

Okay so my "I think" own family members keep hacking into my Google accounts thru wifi so installed a virus protection program that lets me know who is trying to gain access and these same numbers keep popping up and I'm just trying to figure out who it is so I can get my privacy back...

Port 137 (tcp/udp) (13)

Port 137 (tcp/udp) (14)Port 137 (tcp/udp) (15)Port 137 (tcp/udp) (16)

Port 137 (tcp/udp) (2024)

FAQs

What is UDP port 137 used for? ›

Port 137 is utilized by NetBIOS Name service. Enabling NetBIOS services provide access to shared resources like files and printers not only to your network computers but also to anyone across the internet.

What is the difference between port 139 and 137? ›

Port 137 is for providing name services over TCP or UDP for SMB over NetBIOS. Port 138 is for providing diagram services over UDP for SMB over NetBIOS. Port 139 is for providing session services over TCP or UDP for SMB over NetBIOS. Port 445 is for directly-hosted SMB over TCP or UDP without the need of NetBIOS.

Is port 138 TCP or UDP? ›

Well-known ports
PortTCPUDP
138AssignedYes
139YesAssigned
143YesAssigned
151Assigned
127 more rows

Does NetBIOS use UDP? ›

Datagram mode is "connectionless"; NetBIOS datagrams are sent over UDP. A datagram is sent with a "Direct Unique" or "Direct Group" packet if it's being sent to a particular NetBIOS name, or a "Broadcast" packet if it's being sent to all NetBIOS names on the network.

Is NetBIOS still used? ›

It was developed in the 1980s for use on early, IBM-developed PC networks. A few years later, Microsoft adopted NetBIOS and it became a de facto industry standard. Currently, NetBIOS is mostly relegated to specific legacy application use cases that still rely on the suite of communication services.

Should I block NetBIOS? ›

There are many security concerns with NetBIOS; and disabling its support on your network and devices is strongly recommended. 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.

What is port TCP 139 used for? ›

Port 139, primarily used by the Server Message Block (SMB) protocol for file sharing in Windows networks, stands out as a critical point of vulnerability when not properly secured. This port facilitates network communications, allowing computers to share files, printers, and serial ports over a network.

Does syslog use TCP or UDP? ›

Syslog runs on UDP, where syslog servers listen to UDP port 514 and clients (sending log messages) use a port above 1023. Note that a syslog server will not send a message back to the client, but the syslog log server can communicate, normally using port 514.

Does SMB use TCP or UDP? ›

SMB relies on the TCP and IP protocols for transport. This combination allows file sharing over complex, interconnected networks, including the public Internet. The SMB server component uses TCP port 445.

What is the difference between TCP and UDP ports? ›

TCP is best used for direct communication in which a reliable connection is needed, such as web browsing, email, text messaging, and file transfers. UDP is best used for live and real-time data transmission when speed is more important than reliability.

Is port 135 TCP or UDP? ›

Port 135 Details
Port(s)ProtocolService
135tcp,udpmsrpc
135tcp,udploc-srv
135tcpthreat
135tcpthreat
22 more rows

What are UDP ports? ›

A User Datagram Protocol port is an internetworking software abstraction, not a physical thing like a USB port. In Internetworking with TCP/IP , Douglas Comer explains, “We will imagine that each machine contains a set of abstract destination points called protocol ports.

Is port 137 TCP or UDP? ›

Port 137 Details
Port(s)ProtocolService
137tcp,udpnetbios-ns
137tcp,udp
137tcptrojan
137udptrojan
7 more rows

What is port 137 traffic to Microsoft? ›

UDP packets on port 137 are used to perfom a Netbios name lookup. Within Microsoft's Windows file sharing, these lookups are similar to DNS in that they resolve an IP to a computer name and back.

Do I need NetBIOS over TCP IP? ›

NetBIOS over TCP/IP is a networking protocol that allows legacy computer applications relying on the NetBIOS to be used on modern TCP/IP networks. Enabling NetBios might help an attackers access shared directories, files and also gain sensitive information such as computer name, domain, or workgroup.

What do you use UDP ports for? ›

While UDP is used in situations where the volume of data is large and security of data is not of much significance, TCP is used in those situations where security of data is one of the main issues. While the transfer of data, the existence of ports is a matter of high significance.

What is UDP port 3702 used for? ›

Web Services Dynamic Discovery (WS-Discovery) is a technical specification that defines a multicast discovery protocol to locate services on a local network. It operates over UDP port 3702 and uses IP multicast address 239.255. 255.250 (IPV4) or FF02::C (IPV6).

What would UDP be used for? ›

User datagram protocol (UDP) is used for time-critical data transmissions such as DNS lookups, online gaming, and video streaming. This communication protocol boosts transfer speeds by removing the need for a formal two-way connection before the data transmission begins.

What is port 135 UDP used for? ›

Port 135 is used for RPC client-server communication; ports 139 and 445 are used for authentication and file sharing. UDP ports 137 and 138 are used for local NetBIOS browser, naming, and lookup functions.

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