Windows 10 Pro V1803: SMBv1 ‘special traps’

[German]If you depend on the SMBv1 network protocol, you need to pay special attention under Windows 10. Especially Windows 10 V1803 has its own specials regarding SMBv1.


Some background about the SMBv1 problem

Microsoft had already announced since summer 2017 that support for the SMBv1 protocol in Windows 10 will expire. The abbreviation SMB stands for Server Message Block (former names are LAN Manager or NetBIOS protocol), a network protocol for file, print and other server services in computer networks. Version 1 (SMBv1) of the network protocol designed over 30 years ago, and especially the Microsoft implementation, is considered very error-prone and security-critical (see Microsoft plans to deactivate SMBv1 in  Windows 10 V1709 and Stop Using SMB1).

In the meantime there are SMBv2 and SMBv3, so that the use of SMBv1 in Windows networks is no longer absolutely necessary. For example, Windows Vista is no longer dependent on SMBv1 because SMBv2 is used there.

The theory: Windows 10 uninstall unused SMBv1

For new installations of Windows 10 it was at least since Windows 10 V1709 that SMBv1 was deactivated. If devices required SMBv1, the administrator had to activate SMBv1 again via Windows features (see also).

Windows Features SMB 1.0/CIFS

With Windows 10 V1803, however, Microsoft has planned the following: If the SMBv1 client is not used for a total of 15 days (except when the computer is turned off), Windows 10 April Update automatically uninstalls the SMBv1 client (see this Microsoft article and my blog post Windows 10: Scanner fails after update).


But re-enabling SMBv1 in Windows 10 V1803 doesn’t fixed all network issues. Due to a bug, SMBv1 connections didn’t work after a reinstall. This has been fixed with Update KB4284848 (see PSA: Windows 10 V1803: Update KB4284848 brings SMBv1 fix). But that’s not the end.

Windows 10 Pro V1803, the SMBv1 cliff

Already in Windows 10 V1709 SMBV1 was removed and the uninstallation strategy outlined above should work in Windows 10 Home from version 1803. But the subtleties are in the details, as Ned Pyle from Microsoft explains in a tweet (thx to askwoody, who spotted it).

The automatic uninstallation of the SMBv1 protocol when not in use does not work if you reinstall Windows V1803 Pro on a machine. The same applies to in-place upgrades from Windows 10 from earlier Redstone 1/2 versions to Windows 10 V1803 (Redstone 4) (up to 1703) – skipping Windows 10 V1709 (Redstone 3).

However, if Windows 10 Pro V1709 (Redstone 3) is installed and upgraded to Windows 10 V1803, the’Do not use SMBv1, uninstall protocol’ mechanism is activated as described after 15 days. How Windows 10 Home or Enterprise is behave, is left open. Did you say Linux is complicated?

Similar articles:
Microsoft plans to deactivate SMBv1 in  Windows 10 V1709
PSA: Windows 10 V1803: Update KB4284848 brings SMBv1 fix
Microsoft plans a Windows 10 V1803 SMBv1 fix on June 2018


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