The service provider, system administrators, and organization administrators are responsible for the security of each vCloud Director tenant organization.
Securing a vCloud Director tenant organization from external attacks is largely a matter of providing good system-level security, so that external attackers are not able to access tenant resources. The service provider also has to be aware of the possibility that one tenant can attack, or simply interfere with, another. Potential intertenant attack vectors include snooping system-level details of compute, storage, and network resources. Interference, deliberate or not, arises when system resources are shared among tenants (who may be mutually suspicious) and one tenant manages to consume enough of those resources to deny other tenants their expected level of service. This situation is often referred to as the "noisy neighbor" problem.
As described in vCloud Director Architecture and Security Features, vCloud Director is designed to enable transparent sharing of system resources among large numbers of tenants. In general, a service provider is free to deploy system resources in way that maximizes system efficiency while minimizing the potential for downtime. Whenever resources are shared among tenant organizations, the service provider should consider how such sharing could affect various tenant operations, and whether it might enable intertenant attacks.