VM isolation is the use of virtual machines to keep one workload separated from another by giving each tenant its own guest operating system, virtual hardware, and process space. The goal is to limit what one tenant can see or influence if another tenant is compromised or misbehaves. In cloud platforms, this reduces the blast radius of bugs, malware, and misconfiguration.
In security practice, VM isolation matters because it is only one layer of defense. It can block direct code execution across tenants, but it does not automatically solve problems below the guest, such as shared storage, memory reuse, or hypervisor flaws. Attackers may look for side channels, escape bugs, or residual data left on reused disks and snapshots. Defenders strengthen VM isolation with hardened hypervisors, strict resource cleanup, zeroing of recycled storage, and continuous testing of teardown paths. Strong isolation is both runtime separation and careful cleanup after a VM shuts down.