What is a Hypervisor?

A hypervisor is software that allows multiple operating systems to run on a single physical machine by creating and managing virtual machines (VMs). Each VM operates like a separate computer, with its own OS, CPU, memory, and storage, while sharing the same underlying hardware.

Hypervisors abstract and allocate physical resources to VMs, enabling isolation, efficiency, and flexible workload management. They’re a foundational component of cloud infrastructure, enterprise IT, and even some home labs. Common examples of hypervisor technologies include KVM, Xen, VMware ESXi, and Microsoft Hyper-V.

Why is it called a “hypervisor”?

The term hypervisor builds on the word supervisor, which in computing refers to the operating system’s kernel. Since this software layer sits above the OS — managing entire OS instances rather than just processes — it earned the name hyper-visor. It’s a small linguistic tweak that reflects a major architectural leap.

Who invented the hypervisor?

The concept originated at IBM in the 1960s, particularly with systems like the IBM CP-40 and CP-67. These mainframe hypervisors were designed for time-sharing, letting multiple users work on a single machine in isolation.

That same idea — efficiently dividing and controlling compute resources — has come full circle in today’s data centers and cloud platforms.

Do hypervisors improve security and resilience?

Yes — but with caveats.

Security

Hypervisors offer strong isolation between VMs. A compromised guest OS shouldn’t be able to impact others, making hypervisors useful for sandboxing, legacy containment, and secure development environments.

However, the hypervisor itself becomes a high-value target. Exploits like hypervisor escapes can break isolation completely. This makes hypervisor hardening and patching absolutely critical in secure environments. Staying informed about potential vulnerabilities is therefore essential for maintaining a secure virtualised environment.

Resilience

Hypervisors enable live migration, snapshotting, and rapid disaster recovery. If hardware fails, virtual machines can often be moved or restored with minimal downtime — boosting business continuity and service availability.

They also allow precise resource management: VMs can be scaled, paused, or cloned as needed without touching hardware.

Is the hypervisor still relevant?

Yes — and evolving.

Still used?

Yes. Hypervisors remain central to most cloud platforms (e.g., AWS using Nitro, Azure using Hyper-V, VMware vSphere). They’re also heavily used in enterprise IT, critical infrastructure, and types of cybersecurity tooling. Furthermore, hypervisors are finding increasing relevance in edge computing environments to manage virtualised workloads in distributed locations.

What’s changing?

Containers are becoming more common for deploying apps. Platforms like Kubernetes have become the standard for container orchestration, offering speed and agility, though with generally less inherent isolation than VMs.

Modern hypervisors are adapting. Lightweight options like Firecracker, Kata Containers, and gVisor are bridging the gap between containers and VMs — offering both speed and enhanced security by running containers within lightweight virtual machines.

The future?

Hypervisors may fade from view, but not from importance. They’ll underpin secure multi-tenant systems, serverless runtimes, and container stacks — often invisibly. Expect coexistence, not replacement, with hypervisors providing a foundational layer of isolation and security for various higher-level abstractions and legacy systems.

Why does this matter for risk and governance?

If infrastructure resilience, data isolation, or regulatory assurance is one of your objectives, understanding hypervisors is useful — even if you’re not hands-on with tech. They sit at a key control layer in many third-party cloud and SaaS providers.

Look for questions like:

  • Does this system rely on VM-level isolation or container security? How are container workloads isolated?
  • Is the underlying hypervisor patched and monitored for vulnerabilities?
  • Are guest workloads segregated to avoid noisy-neighbor or co-residency risks at the hypervisor level?

Final Thought

Hypervisors are like the plumbing of modern IT: invisible when working well, catastrophic when neglected. For CISOs, risk leaders, and architects, understanding their role helps you ask sharper questions — and spot hidden dependencies in cloud-first environments.

🧭 At Lines of Defence, I explore how foundational tech like this shapes our assumptions about resilience, governance, and control. If you’re curious about where things are going, keep reading or drop me a line.