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 classific