3.5 Virtual Machine Security Considerations

In many ways, virtual servers have security requirements identical to those of physical servers. The same applies to the applications and services they host. Virtualization provides security benefits: each virtual machine has a private security context, potentially with separate authentication and authorization rules, and with separate process, name and file system spaces. Deploying applications onto separate virtual machines provides better security control compared to running multiple applications on the same host operating system: penetrating one virtual machine's OS doesn't necessarily compromise workload and data residing in other virtual machines. Nonetheless, some practices should be kept in mind to prevent virtualization from introducing security vulnerabilities.

One aspect is physical security. Virtual infrastructure is not as 'visible' as physical infrastructure: there is no sticky label on a virtual machine to indicate its purpose and security classification. If a datacenter identifies servers with extremely high security requirements, and physically isolates them in a locked room or cage to prevent tampering or theft of data, then the physical machines hosting their virtualized workloads should be isolated in a similar way.  Even without secured areas, many institutions keep workloads of different security classes on different servers. Those same isolation rules apply for virtual machines. Care should be taken to ensure that the protected virtual machines are not migrated to a server in a less secure location. In the context of Oracle VM, this implies maintaining separate server pools, each with their own group of servers.

These rules of isolation should also be applied to networking: there are no color coded network cables to help staff identify and isolate different routes, segments and types network traffic to and from virtual machines or between them. There are no visual indicators that help ensure that application, management, and backup traffic are kept separate. Rather than plug network cables into different physical interfaces and switches, the Oracle VM administrator must ensure that the virtual network interfaces are connected to separate virtual networks. Specifically, use VLANs to isolate virtual machines from one another, and assign virtual networks for virtual machine traffic to different physical interfaces from those used for management, storage or backup. These can all be controled from the Oracle VM Manager user interface. Ensure that secure live migration is selected to guarantee that virtual machine memory data is not sent across the wire unencrypted.

Additional care must be given to virtual machine disk images. In most cases the virtual disks are made available over the network for migration and failover purposes. In many cases they are files, which could easily be copied and stolen if the security of network storage is compromised. Therefore it is essential to lock down the NAS or SAN environments and prevent unauthorized access. An intruder with root access to a workstation on the storage network could mount storage assets and copy or alter their contents. Use a separate network for transmission between the storage servers and the Oracle VM hosts to ensure its traffic is not made public and subject to being snooped. Make sure that unauthorized individuals are not permitted to log into the Oracle VM Servers, as that would give them access to the guests' virtual disk images, and potentially much more.

All of these steps require controlling access to the Oracle VM Manager and Oracle VM Server domain 0 instances. Network access to these hosts should be on a private network, and the user accounts able to log into any of the servers in the Oracle VM environment should be rigorously controlled, and limited to the smallest possible number of individuals.