Disable SMBv1 on the SMB client
Setting this DWORD value to `4` assigns the Disabled startup type to the `MRxSMB10` driver.
since 0.9.8.11
Purpose
Show registry keys (1)
HKLM\SYSTEM\CurrentControlSet\Services\mrxsmb10\Start
Setting this DWORD value to 4 assigns the Disabled startup type to the MRxSMB10 driver. After the computer is restarted, the driver is no longer loaded and the computer cannot establish SMBv1 connections as an SMB client.
This value affects only the SMBv1 client component. It does not disable the SMBv1 server or uninstall the optional SMBv1 feature. It does not directly disable SMBv2 or SMBv3.
Notes
Security
SMBv1 is an obsolete protocol with known security weaknesses. Preventing outbound SMBv1 connections reduces the attack surface, particularly when the computer encounters an untrusted or compromised SMB server.
This value does not protect against inbound SMBv1 connections if the SMBv1 server component remains enabled.
Possible side effects
The computer can no longer access file shares or devices that support only SMBv1. This can affect legacy NAS devices, operating systems, applications, and embedded equipment.
If MRxSMB10 remains listed as a dependency of the LanmanWorkstation service, disabling only the driver can prevent that service from starting normally. SMB client functionality not limited to SMBv1 may consequently be affected.
Notes
Microsoft documents removal of MRxSMB10 from HKLM\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\DependOnService as an additional part of fully disabling the SMBv1 client. The registry value described here does not perform that accompanying change.
A restart is required for the change to take effect. SMBv1 is already absent by default from many modern Windows installations; when the component is not installed, disabling its driver has no additional protocol effect.
Microsoft documentation
Microsoft Learn: Detect, enable, and disable SMBv1, SMBv2, and SMBv3 in Windows
Microsoft Learn: Protect SMB traffic from interception