Hypervisor¶

Term: Hypervisor (Virtual Machine Monitor, VMM)

Definition: The software layer that creates, runs, and manages virtual machines while coordinating their access to the physical hardware.

Context/Example: VirtualBox, VMware ESXi, and KVM are hypervisors; they decide how much CPU, RAM, and disk each VM gets and enforce isolation.

Related Concepts: Type 1 / Type 2 hypervisor, VM, resource allocation, isolation.

Types of Hypervisors¶

Term: Type 1 Hypervisor (Bare-Metal Hypervisor)

Definition: A hypervisor that runs directly on the physical hardware, with no “normal” host OS underneath.

Context/Example: VMware ESXi or Microsoft Hyper-V Server installed directly on a server; all VMs run on top of this thin hypervisor layer.

Related Concepts: Type 2 hypervisor, full virtualization, multi-tenancy, cloud providers.

Term: Type 2 Hypervisor (Hosted Hypervisor)

Definition: A hypervisor that runs as a normal application on a host OS like Windows, macOS, or Linux.

Context/Example: VirtualBox or VMware Workstation installed in your desktop OS; the hypervisor is “just another program” the OS is running.

Related Concepts: Type 1 hypervisor, host OS, desktop virtualization.

Term: Hypervisor Vulnerability

Definition: A security flaw in the hypervisor that an attacker can exploit to impact multiple VMs or the host.

Context/Example: A bug in ESXi or KVM that lets a guest VM send specially crafted instructions and gain control over the hypervisor process.

Related Concepts: VM escape, patch management, CVE, attack surface.