Windows Server 2025 insecure logons to an SMB server must be disabled.

Insecure guest logons allow unauthenticated access to shared folders. Shared resources on a system must require authentication to establish proper access.

If the following registry value does not exist or is not configured as specified, this is a finding:

Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \SOFTWARE\Policies\Microsoft\Windows\LanmanWorkstation\

Value Name: AllowInsecureGuestAuth

Type: REG_DWORD Value: 0x00000000 (0)

Configure the policy value for Computer Configuration >> Administrative Templates >> Network >> Lanman Workstation >> Enable insecure guest logons to "Disabled".