Q&A: Virtualization Security
by Mirko Zorz - Wednesday, 10 September 2008.
Jim Chou is the Executive VP of Technology for Apani where he is responsible for the strategic technical development of Apani technology and product portfolio development. In this interview he discusses virtualization security.

What are the clear benefits of implementing virtualization?

The benefits of server virtualization are clear and well-documented throughout IT organizations. From an economic perspective, there are obvious benefits in terms of lower capital investment in hardware by consolidation, lower power consumption and a smaller footprint (or the same footprint for a large server farm). Management benefits are also well-documented. Additional servers are easier to add to the data center, because they are based on pre-configured, pre-installed VM images. Management systems from virtualization vendors enable VMs to be moved when their hosts are low on resources, thereby easing the management burden for administrators.

For line of business applications not dependent on high-performance I/O, server virtualization is almost a no-brainer since it allows the IT organization to maximize utilization.

What are the security risks unique to virtualized environments? What can be done to mitigate those threats?

There are two general areas of attack being discussed by security and virtualization professionals. The first is attacks on the hypervisor itself. I believe that attacks on the hypervisor represent an inflated risk, with the risk being largely inflated by vendors looking for a market. The hypervisor is purpose-built and contains relatively few lines of code – and therefore a small attack surface. In fact, while there are some theoretically possible attacks on the hypervisor, there has yet to be a documented attack.

The second revolves around inter-VM communications, and an area where we believe real risk resides. It should be noted that VMs themselves are no less secure than their physical counterparts, but there are several areas of risk with which to be concerned, including:
  • VM sprawl – VMs are so simple to create that many virtualized data centers suffer from VM sprawl. If VMs are created from unpatched images, known vulnerabilities can be exploited.
  • Inter-VM attacks – Each physical host has a “soft-switch” to enable VMs to communicate with one another. Because inter-VM communications do not always leave the physical host, they are unprotected by firewalls and other hardware-based protection. In the event a VM is compromised, it can attack other VMs on the same host without detection from existing tools.
  • Migration of VMs – Some server virtualization packages enable VMs to be migrated while running to different physical hosts. In the event security solutions are not designed to support hot or cold VM migration, policy may cease to protect the VM. Alternatively, the VM may become inaccessible and cause system outages.
Many vendors offer a silo approach to security, offering separate solutions for physical and virtual machines. Security administrators should be cautious of these wares, as they add incremental management tools and can introduce incompatibility.

A more effective option is to leverage cross-platform virtual security solutions. These solutions are designed to support mixed physical/virtual data centers – a reality for many businesses. These software-based solutions offer a centralized management view to simplify policy enforcement. They also ensure policy persistence in the event a physical or virtual machine is migrated to another physical host, or to another location in the builder. Because cross-platform virtual security solutions are based on software, they protect machines regardless of their physical location, directly addressing the threats introduced by VM sprawl, inter-VM communications and migration.


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