Can Others See Your Data?
A major concern most customers have is whether others can see your data. Office 365 is architected as a multitenant service, but that also means that customers do share hardware resources. Office 365 is designed to host multiple tenants securely through data isolation as each tenant is segregated through Active Directory, which isolates customers using security boundaries or silos. This is architected in a manner to help ensure that different companies that share hardware resources—that is, co-tenants—will not have their data accessed or compromised by another tenant that is not associated with that organization.
Microsoft does provide the option for organizations to procure dedicated hardware for an Office 365 deployment if required, but that path, in some cases, seems counterintuitive to the main reason Office 365 exists.