VMware VMCI, or Virtual Machine Communication Interface, is a VMware guest-to-host communication channel that lets software inside a virtual machine exchange data with the host or other VMware components without using ordinary network paths. Because the traffic can stay inside the virtualization layer, it may bypass external firewalls, network sensors, and some packet captures.
In cyber security, VMCI matters because attackers can use it as a quieter command, control, or data-transfer path on VMware-based systems. That can make malicious activity harder to spot if defenders only watch Ethernet traffic. Defenders look for unexpected VMCI use by monitoring VMware telemetry, guest process behavior, and unusual guest/host interactions. In a hardened environment, restricting VMCI to necessary workloads and correlating it with host and hypervisor logs can help reveal abuse.