Despite the strengths of virtualization technologies, you should understand some weaknesses. If you’re planning to take the SY0-501 exam, you’re expected to have a good understanding of virtualization concepts. This includes threats to virtual system security.
For example, can you answer this practice test question?
Q. Administrators frequently create VMs for testing. They sometimes leave these running without using them again after they complete their tests. Which of the following does this describe?
A. VM escape
B. VDI snapshot
C. VM sprawl
D. Type II hypervisor
More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation are available at the end of this post.
Application Cell or Container Virtualization
Application cell virtualization or container virtualization runs services or applications within isolated application cells (or containers). For comparison, the figure shows an example of container virtualization. Notice that the containers don’t host an entire operating system. Instead, the host’s operating system and kernel run the service or app within each of the containers. However, because they are running in separate containers, none of the services or apps can interfere with services and apps in other containers.
Container-based virtualization
A benefit of container virtualization is that it uses fewer resources and can be more efficient than a system using a traditional Type II hypervisor virtualization. Internet Service Providers (ISPs) often use it for customers who need specific applications. One drawback is that containers must use the operating system of the host. As an example, if the host is running Linux, all the containers must run Linux.
Risks Associated with Virtualization
Despite the strengths of virtualization technologies, you should understand some weaknesses. Many people consider virtual machine escape (VM escape) to be the most serious threat to virtual system security. Loss of confidentiality and loss of availability can also be a concern.
VM Escape
VM escape is an attack that allows an attacker to access the host system from within the virtual system. As previously mentioned, the host system runs an application or process called a hypervisor to manage the virtual systems. In some situations, the attacker can run code on the virtual system and interact with the hypervisor.
Most virtual systems run on a physical server with elevated privileges, similar to administrator privileges. A successful VM escape attack often gives the attacker unlimited control over the host system and each virtual system within the host.
When vendors discover VM escape vulnerabilities, they write and release patches. Just as with any patches, it is important to test and install these patches as soon as possible. This includes keeping both the physical and the virtual servers patched.
VM Sprawl
VM sprawl occurs when an organization has many VMs that aren’t managed properly. Most organizations have specific policies in place to ensure physical servers are kept up to date and personnel only make changes to these servers after going through a change management process. These same policies should also apply to virtual servers.
Consider this scenario. Bart creates a VM running a Microsoft Windows Server version to test a software application. After testing the application, he leaves the VM running. Later, Microsoft releases security patches for the server. The IT department tests these patches and applies them to all of the known servers that need them. However, because Bart didn’t tell anyone he was creating the VM, it remains unpatched and vulnerable to attack.
Another challenge with VM sprawl is that each VM adds additional load onto a server. If unauthorized VMs are added to physical servers, they can consume system resources. The servers might become slower and potentially crash.
Loss of Confidentiality
As a reminder, each virtual system or virtual machine is just one or more files. Although this makes it easy to manage and move virtual machines, it also makes them easy to steal.
It’s worth pointing out that many VMs include the operating system and data, just as a physical system would have both the operating system and data on its physical drives. For example, a virtual machine can include a database with credit card data, company financial records, or any type of proprietary data.
Imagine if an administrator became disgruntled. He has access to the systems and as a malicious insider, he can copy the virtual machine, take it home, and launch it on another physical server. At this point, he has access to the system and the data.
Q. Administrators frequently create VMs for testing. They sometimes leave these running without using them again after they complete their tests. Which of the following does this describe?
A. VM escape
B. VDI snapshot
C. VM sprawl
D. Type II hypervisor
Answer is C. VM sprawl occurs when an organization has many VMs that aren’t managed properly. Unmonitored VMs typically won’t get updated and can be vulnerable to attacks.
VM escape is an attack that allows an attacker to access the host system from within the virtual system. A virtual desktop infrastructure (VDI) provides users with virtual desktops hosted on a server.
A VDI snapshot is commonly used to provide users with the same non-persistent desktop that doesn’t save changes.
The VMs might be Type II hypervisors (running as software within a host operating system), but that isn’t relevant to leaving them running and unmonitored.
See Chapter 1 of the CompTIA Security+: Get Certified Get Ahead: SY0-501 Study Guide for more information on implementing virtualization.