[Samba] How to prevent logging into Windows Server with null password or null user and password

[Tompkins, Michael]

I've searched the web and can't find out how to disable Guest/Anonymous logins for samba. I've tried:
Local Group Policy Editor...Security Options: Accounts: Guest account status: Disabled,

but user's with null passwords or null user and password, can still log in. We'd like to only allow users with valid names and passwords to log in.

Thanks,
Mike