To Grasp the Cloud—Fundamental Concepts - Deploying and Managing a Cloud Infrastructure - page 35

Benefits of Hypervisors
There are several factors that can influence utilizing hypervisors to manage and run mul-
tiple incompatible and different operating systems on the same hardware. The guest operat-
ing systems in turn can provide varying provisioning services such as FTP/SFTP servers,
email servers, secure shell connection servers, and more. Some of the benefits of using
hypervisors are listed here:
Expanding Hardware Capabilities A single host machine can do more simultaneous
work. For example, you can launch new services that should be in a segregated environ-
ment and have different security requirements, such as an email server against a Secure
Shell connection.
Costs Because new hardware is not needed for launching a new operating system and ser-
vices, costs can be curtailed and controlled. Moreover, this simplifies management through
consolidation of soft servers.
Control Management Cluster and data center management and installations can be con-
trolled from one platform. A hypervisor, therefore, can act as a management console for
various operating environments (i.e., the OS and its services).
Heterogeneous Environments Hypervisors provide system administrators with the ability
to run complex and operating-system-dependent applications on different hardware and
operating environments.
Reliability and Independence Environments managed via hypervisors offer greater reli-
ability and independence because of two main reasons. First, a hypervisor provides a single
point of management for all operating environments. Any faulty virtual environment can
be easily replaced. Second, hypervisors offer independence from hardware requirements of
different operating systems, thus neutralizing heterogeneity and incompatibility.
Hypervisor Security Concerns
One of the biggest concerns of using hypervisor technology is related to malware and
rootkit auto-installation. An infected hypervisor environment can make such malicious
software hard to detect. This is because the malware could access operations of the operat-
ing system that are managed through the hypervisor. An antivirus tool may also not be of
much advantage because the malware runs below the entire operating system, as claimed
by research at the University of Michigan: SubVirt: Implementing malware with virtual
machines (April 2006).
However, IBM Linux Technology Center disputes such a claim and instead asserts that it
is possible to detect the presence of a hypervisor-based rootkit:
http://virtualization.info/en/news/2006/08/debunking-blue-pill-myth.html
Moreover, companies such as Microsoft research and develop tools that can provide protec-
tion against hypervisor-based rootkits.