5) Build Virtual DMZ’s - For systems deemed to be safe for virtualization, the virtual servers that run together on the same hardware platform should share similar security requirements. Think of these systems as being together on a virtual DMZ network. The virtual machines will likely exist on the same subnet and may communicate with each other to handle transactions. It is preferable to configure hosts in this manner so that they do not need to traverse an external firewall (separate physical system) to communicate with each other.

6) Make network intrusion detection and prevention changes - If multiple virtual machines are using the same network interface cards, keep in mind the extra bandwidth that will be traversing that card. Before you may have had separate servers, each with Gig interfaces, peaking at 80 MB/sec of traffic. Now you will have a Gig interface peaking at 480 MB/sec if you run 6 virtual machines. Your network intrusion protection system may need to be re-architected slightly to keep up with the new demands of this single port.

7) Understand the impact to incident response and forensics plans - When introducing virtual systems into an environment, things like incident response need to be handled a little differently. Your incident response plan must now account for other systems running on the same virtual host. Immediately separate the suspect virtual machine from the others to ensure proper containment. Your system image acquisition process will also need to take into account the differences between nonvirtual and virtual systems.


8) Host intrusion detection and prevention - Host intrusion protection should continue to be in place as it would with a stand-alone server. Be sure to test your intrusion detection and prevention software within the virtual environment. Check with your vendor to be sure it is officially supported when running in a virtual environment.

Does it always make sense to virtualize?

It is important to keep critical authentication and directory services on dedicated systems. In most cases Active Directory domain controllers, RSA authentication manager servers, and RADIUS servers should not be run in a virtualized environment. However, there are exceptions to this, especially with regards to disaster recovery initiatives.

Although some firewall vendors are beginning to provide virtualization-ready solutions, it is best to hold off on virtualizing your firewall servers for now. While the idea of hosting multiple firewalls as virtual servers on a single host is appealing, you are likely running multiple firewalls that serve very different needs—with different security policies and rules. Keep these systems on their own servers for now.