This policy setting determines whether packet signing is required by the SMB client component. If you enable this policy setting, the Microsoft network client computer cannot communicate with a Microsoft network server unless that server agrees to sign SMB packets. In mixed environments with legacy client computers, set this option to Disabled because these computers will not be able to authenticate or gain access to domain controllers. However, you can use this policy setting in Windows 2000 or later environments. Note When Windows Vista?based computers have this policy setting enabled and they connect to file or print shares on remote servers, it is important that the setting is synchronized with its companion setting, Microsoft network server: Digitally sign communications (always), on those servers. For more information about these settings, see the Microsoft network client and server: Digitally sign communications (four related settings) section in Chapter 5 of the Threats and Countermeasures guide. This policy setting determines whether packet signing is required by the SMB client component. Fix: (1) GPO: Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options!Microsoft network client: Digitally sign communications (always) (2) REG: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanWorkstation\Parameters!RequireSecuritySignature