Direct host Server Message Block (SMB) over TCP/IP - Windows Server (2024)

FAQs

What is Server Message Block SMB protocol over TCP IP? ›

SMB serves as the basis for Microsoft's Distributed File System implementation. 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 Server Message Block protocol? The Server Message Block protocol (SMB protocol) is a client-server communication protocol used for sharing access to files, printers, serial ports and other resources on a network. It can also carry transaction protocols for interprocess communication.

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 445 under specific local ports, select TCP and press next.

SMB uses either IP port 139 or 445. Port 139: SMB originally ran on top of NetBIOS using port 139. NetBIOS is an older transport layer that allows Windows computers to talk to each other on the same network. Port 445: Later versions of SMB (after Windows 2000) began to use port 445 on top of a TCP stack.

Step 1: Open control panel Step 2: Navigate to programs and features. Step 3: Click on "Turn Windows features on or off. Step 4: Disable "(Server Message Block) SMB v1"Step 5 : Click ok.

The Server Message Block (SMB) protocol is a network file sharing protocol that allows applications on a computer to read and write to files and to request services from server programs in a computer network.

While disabling or removing SMBv1 might cause some compatibility issues with old computers or software, SMBv1 has significant security vulnerabilities, and we strongly encourage you not to use it.

Inbound connections to a computer

For Windows clients and servers that do not host SMB shares, you can block all inbound SMB traffic by using the Windows Defender Firewall to prevent remote connections from malicious or compromised devices. In the Windows Defender Firewall, this includes the following inbound rules.

While port 139 and 445 aren't inherently dangerous, there are known issues with exposing these ports to the Internet. You can check if a port is open by using the netstat command. There is a common misconception that an open port is dangerous.

Note that blocking TCP 445 will prevent file and printer sharing, including over apps – if this is required for business, you may need to leave the port open on some internal firewalls or use encryption keys.

How to check if port 445 is blocked? ›

On the diagnostics page, you can check the status for both ports 445, and 1433, and internet speed. If either 445 or 1433 are blocked you will receive an error when performing the respective test. For internet speed, if you are in an office environment, we recommend a minimum of 50 Mbps each way (Download & Upload).

Despite its utility, TCP 445's open nature can also be its Achilles' heel, exposing networks to unauthorized access and malicious exploits. Cybercriminals can leverage vulnerabilities in this port to inject malware, ransomware, or carry out Denial of Service (DoS) attacks.

Server message block (SMB) is a client/server communication protocol that provides shared access to files, whole directories, and network resources such as printers across a network. It is also used to carry transaction protocols for authenticated interprocess communication.

Modern Windows versions rely on port 445 for SMB traffic, making it a critical component of contemporary network architectures.

The Get-SmbConnection cmdlet retrieves the connections established from the Server Message Block (SMB) client to the SMB servers. Users can connect to an SMB share using credentials different than the associated logon credentials so that there will be a connection listed per share per user logon per credential used.

SMB has always been a network file sharing protocol. As such, SMB requires network ports on a computer or server to enable communication to other systems. SMB uses either IP port 139 or 445.

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.

The SMB protocol (the Server Message Block) is a network protocol that enables users to communicate with remote computers and servers (e.g., to share resources or files). It's also referred to as the server/client protocol because the server has a resource that it can share with the client.

SMB Encryption offers an end-to-end privacy and integrity assurance between the file server and the client. It provides this security regardless of the networks traversed, such as wide area network (WAN) connections maintained by non-Microsoft providers.