The host system is the main computer or operating system that runs virtualization software and the guest machines inside it. In a desktop lab, the host provides the real hardware, storage, network access, and user session, while each virtual machine is isolated as a guest.
In cyber security, the host is the prize in a guest-to-host breakout. If an attacker can escape the virtual machine, they may execute code on the host system, reach local files, install malware, or interfere with other workloads. That is why host protection matters even when guests are treated as disposable or untrusted. Defenders reduce risk by patching the hypervisor, limiting guest privileges, disabling unnecessary integration features, and separating sensitive host data from experimental virtual machines.