What does "attacks on the hypervisor" refer to?

Attacks on the hypervisor specifically refer to compromises that occur on the hypervisor itself. A hypervisor is a type of virtualization technology that allows multiple virtual machines (VMs) to run on a single physical host by managing the resources and interactions between the guest operating systems and hardware.

When an attack targets the hypervisor, it poses a significant threat because it can lead to unauthorized access across all virtual machines hosted on that hypervisor. Given that the hypervisor operates at a lower level than the guest OS, if an attacker gains control over it, they may manipulate the VMs, extract sensitive data, or even launch further attacks. The impact of such breaches can be extensive, affecting the security isolation that virtualization provides.

In contrast, the other answer choices focus on less comprehensive or more specific areas. Attacks on the underlying operating system or user negligence do not directly address the unique threats posed to the hypervisor itself. Similarly, network-based attacks typically involve external threats and may not target the hypervisor specifically. Thus, recognizing that compromises occurring directly on the hypervisor constitute a distinct and critical concern in cloud security is essential for understanding the threat landscape within virtualized environments.