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What's the impact of using 'SYSTEM' authentication of a service when accessing SMB Shares

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Applies to

  • ONTAP 9
  • Windows Services

Answer

  • When a service uses SYSTEM, authentication is presented to the SMB server as the machine account user.  
  • The Windows OS determines if its possible to use Kerberos or if it must use NTLM to authenticate
  • ONTAP allows machine accounts to authenticate via NTLM & Kerberos
  • If the client uses NTLM to authenticate:
    • Each CIFS session will require the SMB server to reach out to the domain controller (DC) to validate the credentials passed
    • If a CIFS session is not reused, each file operation will open a new CIFS session and require credential validation via the DC
      • A service that reads {x} files will cause {x} password validations from the SMB server to the DC (potentially very taxing)
      • This issue compounds exponentially when the DC begins to slow down from the excess validation, potentially resulting in high authentication latency for new sessions
  • If the client uses Kerberos to authenticate, the client will simply resubmit the service ticket when opening new sessions
    • While this incurs a minimal penalty to decrypt the ticket, this authentication workflow is generally less susceptible to latency in addition to being more secure

Additional Information

 

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