Control VM-VM communications

The Virtual Machine Communication Interface (VMCI) provides a communication channel between a VM and the host, or between two or more VMs on the same host. In vSphere 6.5, VMCI is disabled by default.

Of course, each VM can talk to others by using the virtual network, so be sure to enforce network segregation with VLAN at the portgroup level, or, if possible, micro-segmentation with NSX.