Digitally sign server communications (when possible)
Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options
If this policy is enabled, it causes the Windows 2000 Server Message Block (SMB) server to perform SMB packet signing.
This policy is disabled by default on workstation and server platforms in Local Computer Policy. This policy is enabled by default on Domain Controllers in the Default Domain Controllers Group Policy object (GPO).
See Digitally sign client communications (always) for further details about using digital signatures in client/server communications.