CISA: Certified Information Systems Auditor

Antivirus protection only on guest operating systems leaves the shared host and hypervisor layer unprotected. A compromise at that layer can undermine isolation and affect multiple virtual machines, making it a broader and more severe exposure than the listed patching intervals or the presence of different guest operating systems. NIST guidance treats the hypervisor, host, and guest operating systems as security-relevant components of the virtual infrastructure.