smb protocol port - Brave Search

varonis.com › blog › smb-port

What is an SMB Port + Ports 445 and 139 Explained

September 14, 2023 - An SMB port is a network port commonly used for file sharing. IBM programmer Barry Feigenbaum developed the Server Message Blocks (SMB) protocol in the 1980s for IBM DOS. SMB continues to be the de facto standard network file sharing protocol ...

upguard.com › blog › smb-port

What is an SMB Port? A Detailed Description of Ports 445 + 139 | UpGuard

July 7, 2025 - SMB still uses port 445. This proved to be problematic as CIFS was a notoriously chatty protocol that could ruin network performance due to latency and numerous acknowledgments.

Videos

SMB Protocol Security Measures: SMB Alternative Ports - YouTube

What is the Server Message Block (SMB) Protocol? - YouTube

January 11, 2025

SMB Ports Explained: 445 and 139 - Learn the difference - YouTube

January 5, 2022

What is SMB protocol? - YouTube

January 3, 2023

Le protocole SMB pour les débutants - YouTube

September 14, 2021

What is an SMB Port? What is Port 445 and Port 139 used for? - YouTube

August 12, 2020

netwrix.com › home › resources › blog › what are smb ports, port 139 & port 445?

What are SMB Ports, Port 139 & Port 445? | Netwrix

May 30, 2025 - SMB operates over TCP port 445 and enables shared access to files, printers, and serial ports among devices on a network. Moreover, its core function of resource sharing, enables SMB to be utilized for following use cases: Involving mail slots ...

Microsoft Learn

learn.microsoft.com › en-us › troubleshoot › windows-server › networking › direct-hosting-of-smb-over-tcpip

Direct host Server Message Block (SMB) over TCP/IP - Windows Server | Microsoft Learn

SMB 1.0 and older CIFS traffic supported the NetBIOS over TCP (NBT) protocol supported the UDP transport, but starting in Windows Vista and Windows Server 2008 with SMB 2.0.2, requires TCP/IP over port 445.

Server Message Block

network communication protocol for providing shared access to resources

Server Message Block (SMB) is a communication protocol used to share files, printers, serial ports, and miscellaneous communications between nodes on a network. On Windows, the SMB implementation consists of two vaguely … Wikipedia

en.wikipedia.org › wiki › Server_Message_Block

Server Message Block - Wikipedia

1 week ago - Server Message Block (SMB) is a communication protocol used to share files, printers, serial ports, and miscellaneous communications between nodes on a network. On Windows, the SMB implementation consists of two vaguely named Windows services: "Server" (ID: LanmanServer) and "Workstation" (ID: ...

Features History Specifications Third-party implementations Security Further reading

SecurityScorecard

securityscorecard.com › home › smb port numbers: a guide to optimizing and securing your network

SMB Port Numbers: A Guide to Optimizing and Securing Your Network

March 18, 2026 - Port 445 allows SMB to operate directly over TCP/IP, bypassing the older NetBIOS layer, which is less secure and more complex. This transition underscores the importance of adapting to newer protocols to enhance network security and performance.

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superuser.com › questions › 1587386 › is-port-445-enough-for-smb

networking - Is port 445 enough for SMB? - Super User

Yes, modern SMB (especially v2/v3) runs only on TCP port 445. However, Windows clients may also expect the server to be pingable, i.e. respond to ICMP Echo, before they even attempt a SMB connection.

Also, it could be that Windows implicitly maps all local address to a magic loopback connection that bypasses the TCP/IP stack entirely and is therefore unaware of your SSH tunnel. I would definitely recommend an IP-level VPN instead.

Only very old clients, Windows 9x era and older, will expect TCP port 139 instead (and possibly the NetBIOS Datagram service on UDP 137-138).

Recently, Microsoft has announced an experimental SMB-over-QUIC which can use UDP port 443 as alternative. This is not yet publicly available.

I would say the answer is that you do need TCP port 139 open. This question came up in Google for me while researching the ports necessary to open on our corporate firewall for an SMB connection to Azure Files (from a different virtual network separated by a firewall) and after looking at the firewall deny logs, I can confirm that we see both 139 and 445 blocked by the firewall for our SMB version 3.1.1 connection to the storage account share.

Edit: After some more research, I found this article which states that NetBT (NetBIOS over TCP/IP) uses port 139. The port 445-only implementation of SMB is called Direct host SMB over TCP/IP

It may be that your server side setting is still trying to use NetBT and you need to follow the steps on the second link above to disable NetBT so that the server will exclusively work on port 445.

superuser.com › questions › 974802 › what-ports-do-i-have-to-open-for-smb-sharing

networking - What ports do I have to open for SMB sharing? - Super User

SMB Ports [File Sharing]

Protocol: tcp/udp
Ports:
137: netbios-ns
138: netbios-dgm
139: netbios-ssn
445: smb-ds

UK Government Security

security.gov.uk › home › services & resources › cyber services in government › domain and vulnerability knowledge base › open port 445: server message block (smb)

Open port 445: Server Message Block (SMB) - UK Government Security - Beta

September 10, 2025 - It operates over port 445 (SMBv3, SMBv2) and ports 137-139 (SMBv1 over NetBIOS).

builtin.com › software-engineering-perspectives › smb-port

What Are SMB Ports? | Built In

A tutorial on what the SMB protocol is and how it works. | Video: NordVPN · A server message block (SMB) port is a network port through which the SMV protocol enables file and resource sharing between networked devices.

petri.com › home › windows client os › windows file sharing with smb: port 445, 139, 138, and 137 explained

Windows File Sharing with SMB: Port 445, 139, 138, and 137

March 24, 2026 - The ‘relationship’ – they are both used for SMB file sharing, but the more modern TCP/IP port, 445, is the default and recommended for new installations of Windows (client and server), whereas port 139 requires NetBIOS to function.

cyberengage.org › post › managing-and-securing-smb-protocol

Managing and Securing SMB Protocol

July 11, 2024 - Configure routers and firewalls to block SMB sessions with TCP port 445 and NetBIOS ports TCP/UDP 135-139. Deploy client systems on Private VLANs (PVLANs): PVLANs can control and restrict inbound SMB traffic to client machines, allowing outbound ...

sslinsights.com › home › wiki › what is port 445: all about smb port 445

What is Port 445: All About SMB Port 445

March 31, 2026 - Port 445 is a vital component of the SMB protocol, enabling Windows networking and resource-sharing functions. However, due to its ubiquitous presence and connection to critical systems, attackers also heavily target it.

windowstechno.com › home › ms windows server

SMB Port - WindowsTechno

May 1, 2023 - SMB is a network file and resource sharing protocol that uses a client-server model that means where clients request a file, and the server provides it to the client. Port 445 is used by Microsoft Directory Services for Active Directory (AD) ...

SecurityScorecard

securityscorecard.com › home › the essential guide to smb port configuration for enhanced network security

The Essential Guide to SMB Port Configuration for Enhanced Network Security - SecurityScorecard

March 30, 2026 - This shift not only simplifies network configurations by eliminating the need for NetBIOS but also enhances security and performance by streamlining the SMB communication process. The evolution from Port 139 to Port 445 reflects the ongoing ...

0xffsec.com › handbook › services › smb

SMB (Server Message Block) Service Enumeration | 0xffsec Handbook

July 3, 2022 - It also provides an authenticated IPC (inter-process communication) mechanism.1 Windows SMB Ports and Protocols # Originally, in Windows NT, SMB ran on top of NBT (NetBIOS over TCP/IP), which uses ports UDP 137 and 138, and TCP 139.

myworkdrive.com › home › blog › smb port: secure remote access alternatives and best practices

SMB Port: Secure Remote Access Alternatives and Best Practices | MyWorkDrive

March 4, 2025 - The SMB port is essentially the network endpoint responsible for the SMB protocol’s communication. Older Windows systems often use port 139 (NetBIOS over TCP/IP), while more modern systems rely on port 445 (SMB over TCP).

curl.se › docs › manpage.html

curl - How To Use

curl is a tool for transferring data from or to a server using URLs. It supports these protocols: DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, MQTTS, POP3, POP3S, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS and WSS.

The Windows Club

thewindowsclub.com › the windows club › general › what is an smb port? what is port 445 and port 139 used for?

What is an SMB Port? What is Port 445 and Port 139 used for?

While Port 139 is known technically as ‘NBT over IP’, Port 445 is ‘SMB over IP’. SMB stands for ‘Server Message Blocks’. Server Message Block in modern language is also known as Common Internet File System.

Published December 25, 2025

reddit.com › r/sysadmin › smb using tcp port 52008 - why?

r/sysadmin on Reddit: SMB using TCP port 52008 - Why?

July 6, 2017 -

I have a Server 2016 VM which is connected to SMB share on a Server 2016 Failover Cluster File Server(s). One of the datastreams is attempting to connect to TCP port 52008 on the Failover Cluster, but is blocked by a firewall which sits in-between. SMB appears to be working fine with this connection blocked. If I run netstat on the active cluster node, it shows that the clussvc.exe process is listening on this port.

Does anyone know why SMB is trying to use this port? And what exactly this port is used for? I've tried googling it but can't seem to find anything.

I would assume because it is configured to do so? Ports are just numbers, they aren't specific bound to a certain service. While there are well known ports < 1024, 52008 certainly isn't one of them. Given that is >49152, I would expect it to be a dynamically chosen port. Maybe the main protocol (SMB) is used to negotiate another connection on a higher port? This kind of behaviour somewhat common with old protocols (ftp) and a major pain in the ar** to configure in your firewall.

What are the chances the cluster server is actually the source of the request, 52008 is the random ephemeral client port it used, the 2016 VM is the destination, the destination port is a standard SMB port, and the firewall blocked the connection because the session expired from the session table? Give us the port from that blocked connection for the 2016 VM and look at whatever log field provides the reason for why the connection was blocked.