Archive for category Security

Webcast: “Understanding and Managing VM Sprawl”

The idea of virtual machine “sprawl” – the rapid proliferation of VMs without adequate IT oversight or management – seems to be a popular one.  I have written and spoken on this topic before, but there have been enough changes in the tools and implementation methods for server virtualization to merit an updated presentation.  That’s the topic of a recent webcast that I recorded for TechTarget’s site. 

The webcast is titled “Understanding and Managing VM Sprawl”.  An archived version is available for viewing at no cost (though registration is required).  Here’s a brief abstract of the topic:


Virtualization can help address many of IT’s biggest headaches, but it can also lead to a problem known as "VM sprawl" – the rapid proliferation of VMs without sufficient IT oversight.  The result is an environment that doesn’t meet security or administration requirements, putting applications, services, and data at risk.

This webcast will provide an overview of VM sprawl – its root causes and related issues, along with ways to mitigate the main issues.  Specifically, it will provide best practices for managing the entire virtual machine life cycle (from deployment to retirement) and details related to tracking VMs in the environment.  The webcast will then describe how automated virtualization management solutions can help provide all of the benefits of virtualization with minimum administrative overhead.

The content is targeted towards IT managers and higher-level IT people.  It focuses on virtualization management strategies, though there’s a good amount of technical depth.  The presentation is roughly 45 minutes in length.  I hope you find it useful, and feel free to post questions or comments here.

Managing Hyper-V Security

I still remember some of my first questions when working with an early test version of Hyper-V (previously known under a wide variety of different names).  OK, I admit that it wasn’t all that long ago.  One of my main questions was related to managing permissions for virtual machines.  After all, not every user (or administrator) should have full permissions on each VM.  Well, Hyper-V does provide flexible and manageable methods for setting up roles and permissions. 

My recently article, Managing Hyper-V’s Security Permissions, describes the details.  From the introduction:

The burdens of managing security permissions are rarely seen as exciting, but they’re an essential duty to which we systems administrators are sworn to carry out. In this tip, I’ll talk about how you can configure and manage permissions for your Hyper-V host servers.

We all rely on a variety of different security methods to ensure that only authorized users can access data center resources. Specific components of overall security range from physical access limitations to network authentication and permissions management. Virtualization brings with it some new requirements, namely the ability to specify which types of actions users can take on host systems.

It’s certainly possible for administrators to manage virtual machines when they don’t have access to the guest OSes themselves. The ability to granularly define authorization rules is essential for production servers. Fortunately, Hyper-V provides methods for defining and maintaining these permissions. But, as you’ll soon see, it’s not an entirely intuitive approach.

The article provides details, steps, and screenshots that help describe the use of the powerful (but unfortunately nick-named) AzMan.

Virtualization Security: Pros and Cons

This article was first published on

Historically, organizations have fallen into the trap of thinking about security implications after they deploy new technology. Virtualization offers so many compelling benefits, that it’s often an easy sell into IT architectures. But what about the security implications of using virtualization? In this tip, I’ll present information about the security-related pros and cons of using virtualization technology. The goal is to give you an overview of the different types of concerns you should have in mind. In a future article, I’ll look at best practices for addressing these issues.

Security Benefits of Virtualization

There are numerous potential benefits of running workloads with a VM (vs. running them on physical machines). Figure 1 provides an overview of these benefits, along with some basic details.


Figure 1: Virtualization features and their associated security benefits.

Since virtual machines are created as independent and isolated environments, systems administrators have the ability to easily configure them in a variety of ways. For example, if a particular VM doesn’t require access to the Internet or to other production networks, the VM itself can be configured with limited connectivity to the rest of the environment. This helps reduce risks related to the infection of a single system affecting numerous production computers or VMs.

If a security violation (such as the installation of malware) does occur, a VM can be rolled back to a particular point-in-time. While this method may not work when troubleshooting file and application services, it is very useful for VMs that contain relatively static information (such as web server workloads).

Theoretically, a virtualization product adds a layer of abstraction between the virtual machine and the underlying physical hardware. This can help limit the amount of damage that might occur when, for example, malicious software attempts to modify data. Even if an entire virtual hard disk is corrupted, the physical hard disks on the host computer will remain intact. The same is true for other components such as network adapters.

Virtualization is often used for performing backups and disaster recovery. Due to the hardware-independence of virtualization solutions, the process of copying or moving workloads can be simplified. In the case of a detected security breach, a virtual machine on one host system can be shut down, and another “standby” VM can be booted on another system. This leaves plenty of time for troubleshooting, while quickly restoring production access to the systems.

Finally, with virtualization it’s easier to split workloads across multiple operating system boundaries. Due to cost, power, and physical space constraints, developers and systems administrators may be tempted to host multiple components of a complex application on the same computer. By spreading functions such as middleware, databases, and front-end web servers into separate virtual environments, IT departments can configure the best security settings for each component. For example, the firewall settings for the database server might allow direct communication with a middle-tier server and a connection to an internal backup network. The web server component, on the other hand, could have required access via standard HTTP ports.

This is by no means a complete list of the benefits of virtualization security, but it is a quick overview of the security potential of VMs.

Potential Security Issues

As with many technology solutions, there’s a potential downside to using virtual machines for security. Some of the risks are inherent in the architecture itself, while others are issues that can be mitigated through improved systems management. A common concern for adopters of virtual machine technology is the issue of placing several different workloads on a single physical computer. Hardware failures and related issues could potentially affect many different applications and users. In the area of security, it’s possible for malware to place a significant load on system resources. Instead of affecting just a single VM, these problems are likely to affect other virtualized workloads on the same computer.

Another major issue with virtualization is the tendency for environments to deploy many different configurations of systems. In the world of physical server deployments, IT departments often have a rigid process for reviewing systems prior to deployment. They ensure that only supported configurations are setup in production environments and that the systems meet the organization’s security standards. In the world of virtual machines, many otherwise-unsupported operating systems and applications can be deployed by just about any user in the environment. It’s often difficult enough for IT departments to know what they’re managing, let alone how to manage a complex and heterogeneous environment.

The security of a host computer becomes more important when different workloads are run on the system. If an unauthorized user gains access to a host OS, he or she may be able to copy entire virtual machines to another system. If sensitive data is contained in those VMs, it’s often just a matter of time before the data is compromised. Malicious users can also cause significant disruptions in service by changing network addresses, shutting down critical VMs, and performing host-level reconfigurations.

When considering security for each guest OS, it’s important to keep in mind that VMs are also vulnerable to attacks. If a VM has access to a production network, then it often will have the same permissions as a physical server. Unfortunately, they don’t have the benefits of limited physical access, such as controls that are used in a typical data center environment. Each new VM is a potential liability, and IT departments must ensure that security policies are followed and that systems remain up-to-date.


Much of this might cast a large shadow over the virtualization security picture. The first step in addressing security is to understand the potential problems with a particular technology. The next step is to find solutions. Rest assured, there are ways to mitigate these security risks. That’s the topic of my next article, “Best Practices for Improving VM Security.”

Improving VM Security: Best Practices

This article was first published on

In my previous Tip, “Pros and Cons of Virtualization Security”, I described many considerations that IT organizations should keep in mind when planning to deploy virtual machines. To put it simply, the goal was to better-define the problem. In this Tip, I’ll present some best practices for managing security for virtualization.

Assessing Risks

Before we dive further into technical details of securing VMs, it’s important to consider the potential security vulnerabilities that are relevant to a particular host and guest OS. Particular questions to ask include:

  • Does the guest of host contain sensitive information such as logon details or sensitive data? If so, how is this information protected?
  • Does the VM have access to the Internet?
  • Can the VM access other production computers?
  • Is the Guest OS running a supported operating system version?
  • Are host and guest OS’s updated automatically?

Answering each question can help clue you in to issues that may need to be addressed. For example, non-networked VMs that reside on a test network will likely have different security requirements from those that are running in a production environment. Let’s look at some details.

Implement Minimal Permissions

A fundamental aspect of maintaining security is to provide users and systems administrators with the minimal permissions they need to complete their jobs. Figure 1 provides an overview of the types of permissions that should be configured.


Figure 1: Types of permissions to consider when securing virtualization

On virtualization hosts, for example, only certain staff members should be able to start, stop, and reconfigure VMs. In addition, it’s important to configure virtual applications and services using limited system accounts. Finally, you should take into account the real requirements for VM configurations. For example, does every VM really need to be able to access the Internet? If so, what is the reason for this? Remember, in the case of a security breach, you want to minimize the number and types of systems that may be affected.

Virtual Machines are still “machines”

Whether an operating system is running on a physical machine or within a virtual one, it still should be regularly updated. Most IT organizations have already invested in some type of automated patch and update deployment process. With virtualization, there are a couple of additional challenges: First, IT departments must be aware of all VMs that are deployed in the environment. Second, each guest OS must be either protected by the update management solution, or must be kept up-to-date manually. Regardless of the approach, systems administrators should keep in mind the time and effort required.

Enforce Consistency and Quality

Simpler environments are much easier to manage than ones in which there is a huge variation in the number and types of systems that are supported. Whenever possible, IT departments should create a base library of reference virtual machines from which users and systems administrators should start. These base images should be verified to meet the IT department’s policies and must be kept up-to-date. Of course, it’s likely that some workloads require deviations from standard deployments. In those cases, IT departments must remain involved in the deployment of all new virtual machines (or, at least those that will have access to production resources).

Managing Moving Targets

The process of moving virtual machines between host servers is usually as simple as performing file copy operations. When a VM is moved, it is important for all relevant security settings and options to move with it. For example, permissions set on virtual hard disk files, and network access details, should be recreated on the target platform. Figure 2 provides some examples of relevant configuration settings to consider.


Figure 2: Security-related settings to consider when moving VMs

Security through Education

Even though the basic concept of virtualization technology is well-planted in most peoples’ minds, users and systems administrators are often confused about the potential use (and misuse) of virtual machines. IT departments, therefore, should verify that their staff is aware of the potential security risks related to deploying new VMs. For most practical purposes, deploying a new VM is similar to deploying a new physical server (though it’s often quicker, cheaper, and easier).

Using Third-Party Solutions

It’s no secret that virtualization technology creates additional burdens related to security. Numerous third-party vendors understand this and have either updated their existing enterprise management tools to include virtualization or have created totally new solutions with innovative approaches to limited vulnerabilities. The focus of this article is on best practices, but when it comes to implementation, IT departments should consider evaluating these various tools.


Overall, organizations can realize the benefits of using virtualization to improve security. However, they will need to be diligent in the creation and deployment of new VMs, as well as with the maintenance of VMs after they’re deployed. As with many other IT solutions, you’ll need to focus on management in order to get the best benefits while minimized vulnerabilities. It’s not an easy job, but it certainly can be done.