Windows 2012R2 backup job fails with "Error: Invalid Signature"

Applies to

• SteelStore
• NetApp Cloud Backup (AltaVault)
• Windows 2012 or Windows 8
• All versions of SteelStore 
• AltaVault versions 4.0.x and 4.1.x
• AltaVault version 4.2 and later supports SMB secure negotiation with FSCTL_VALIDATE_NEGOTIATE_INFO signed IOCTL.  It is not necessary to disable this feature if the AltaVault is running 4.2 or later.

Issue

A Windows 2012R2 backup job fails with the following error message:
Error: Invalid Signature