The components of a vSphere environment are secured out of the box by several features such as authentication, authorization, a firewall on each ESXi host, and so on. You can modify the default setup in many ways. For example, you can set permissions on vCenter objects, open firewall ports, or change the default certificates. You can take security measures for different objects in the vCenter object hierarchy, for example, vCenter Server systems, ESXi hosts, virtual machines, and network and storage objects.
A high-level overview of different areas of vSphere that require attention helps you plan your security strategy. You also benefit from other vSphere Security resources on the VMware Web site.