Server virtualization will become a dominant factor in the next three to five years in an effort to reduce operating costs and simplify business. One highly popular trend is using virtualization for data center consolidation. Companies are consolidating everything from Web servers to the servers that run CRM applications, all in an effort to streamline operations and create efficiency across-the-board.

The consolidation of physical assets to form a heterogeneous environment, while significantly reducing overhead, sounds like a very attractive proposal for any CIO. However, it also introduces additional problems that can substantially increase security risks.

Simply put the aggregation of multiple functions and resources into a single physical platform will not only increase your overall risk, but introduce a single point of failure. This holds especially true if the system has functions relating to the storage and retrieval of sensitive information.

Decisions to adopt virtualization aren't primarily driven from a security viewpoint, but from business enablement. Thus, administrators may not fully understand the risks and implications associated with the deployment of virtualization.

This article will look at several key issues related to the evolving threat landscape and offer advice on how to mitigate these threats.

Virtualization Security: It Starts with Hyperjacking
When looking at the risks inherent in virtualization, we need to understand a bit about the basic architecture - starting with the hypervisor that represents the primary abstraction layer between the physical hardware and the virtual machines (VMs) that are running.

While being able to consolidate resources saves money, it introduces the possibility of "hyperjacking" - malicious control of the hypervisor.

The hypervisor represents a single point of failure when it comes to the security and protection of sensitive information. Theoretically, if this layer is compromised, all the VMs that are running could be accessed by the bad guys. This substantially increases exposure, because it gives hackers another access point to a company's internal database.

But if a hacker compromises a Web server connected to a customer back-end database via a SQL injection, only the information at that source is compromised, reducing the overall impact of the breach. However, virtualization by its nature puts multiple servers and multiple data sources at risk, substantially increasing the degree of risk.

For example, if a company has a clustered group of SQL servers running on the same hypervisor, hackers could target and compromise that layer through a number of different ways, such as subverting the hypervisor with targeted malware (see Figure 1).

Portability Issues
The virtual machine is essentially a file or an image stored on a hard disk. It provides the network administrator with the flexibility and control to move a virtual system from one physical platform to another. And there are tools to assist in migrating active VMs to other live physical servers without interruption. However, because the machine exists as a file, it's subject to attack by viruses and other malware designed to infect the associated file formats (e.g., VMDK, VHD, etc.).

Furthermore, the VM can be accessed offline by remounting the image, allowing the hacker to gain access to the applications and the data stored in them. Offline brute-force dictionary attacks are now possible thanks to the portability that virtualization offers.

Loss of Visibility
Because virtualization fundamentally changes the way that infrastructure is deployed, losses in visibility can occur since the resources are consolidated into a single system. This increases complexity in terms of accurately logging security events.

Tools that were once designed for monitoring access to physical servers now have to be redeployed and reconfigured to monitor multiple aspects of the system, not just the host operating system but the VMs running on top.

It's important to rethink your strategy to include methods for monitoring access to resources.

Strategies for Mitigating Your Risk
When considering a strategy to minimize the risks associated with virtualization, a holistic approach is best - meaning multiple methodologies should be used to thwart hyperjacking.

Because we are dealing with machines within machines, we have to pay special attention to protecting the virtual machine as well as the core architecture - essentially the host operating system running the hypervisor. In this context, further attacks are likely to come from within. In other words, hackers may attempt to subvert the hypervisor to inject targeted malware in an effort to gain access to the VMs.

Fortunately, several different technologies exist that administrators can use to implement a strategy to proactively thwart possible attacks. They include:

• Database Monitoring: Technologies exist to monitor SQL and Oracle databases for suspicious activity (access from unauthorized users, script insertion, SQL statement execution, etc.). Monitoring is only part of the equation in detecting an actual breach in progress. If hackers subsequently decide to access the information stored in your databases, besides extracting the data in real-time, database monitoring will increase the odds of discovering unauthorized access.
• Network Intrusion Detection: Intrusion detection technologies, in addition to other methods, can be used to detect anomalous traffic and behavior that might be associated with an attack.
• Hardening Critical Assets: You can minimize your exposure and risk by hardening critical assets (in this case the host system). In other words, you remove non-essential functionality such as services, applications, and ports that both add to the complexity, but introduce additional risk.

It's important that we take a proactive approach when developing a security plan for a virtual network because the rate at which new malware appears outweighs the capabilities of anti-malware labs to keep up with new threats. The best security policy should include preventive strategies designed for mitigating threats to virtualization.