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Port 137 Details


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Port(s) Protocol Service Details Source
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
W32.Crowt.A@mm (01.23.2005) - mass mailing worm, opens a backdoor, logs keystrokes. Uses ports 80 and 137.
W32.Reidana.A (03.27.2005) - 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).
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,udp netbios-ns NETBIOS Name Service IANA
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
11 records found
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Related ports: 135  138  139  445  

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External Resources
SANS Internet Storm Center: port 137

Notes:
Well Known Ports: 0 through 1023.
Registered Ports: 1024 through 49151.
Dynamic/Private : 49152 through 65535.

TCP ports use the Transmission Control Protocol. TCP is the most commonly used protocol on the Internet and any TCP/IP network. Whereas the IP protocol deals only with packets, 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, a communications protocol for the Internet network, transport, and session layers. Like TCP (Transmission Control Protocol), UDP is used with IP (the Internet Protocol) and makes possible 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, where dropping some packets is preferable to waiting for delayed data.

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