To increase the security of your ESXi hosts, you can put them in lockdown mode. In lockdown mode, operations must be performed through vCenter Server by default.
Starting with vSphere 6.0, you can select normal lockdown mode or strict lockdown mode, which offer different degrees of lockdown. vSphere 6.0 also introduces the Exception User list. Exception users do not lose their privileges when the host enters lockdown mode. Use the Exception User list to add the accounts of third-party solutions and external applications that need to access the host directly when the host is in lockdown mode. See Specify Lockdown Mode Exception Users.