The more privileged lower layer in an IaaS stack is occupied by the:

1. IaaS hands the customer virtual machines. 2. Something beneath them must create and separate them. 3. The lower and more privileged layer is occupied by the Virtual Machine Monitor, also called the hypervisor. 4. So the answer is the hypervisor. _Source: NIST SP 800-146, 'Cloud Computing Synopsis and Recommendations'_