Audit use of all user rights including Backup and Restore
Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options
Determines whether to audit every use of user rights including Backup and Restore.
If you enable this policy, and if the Audit privilege use policy is enabled and in effect, then any instance of user rights being exercised will be recorded in the security log.
If you disable this policy, when users use Backup or Restore privileges, those events will not be audited even when Audit Privilege Use is enabled. You should disable this policy if you want to contain the growth of the security log.
This policy is defined by default in Local Computer Policy where it is disabled by default.