This document discusses hybrid cloud computing and related security aspects and challenges. It begins by outlining why cloud computing is attractive due to cost savings and capabilities like data protection and on-demand services. However, cloud also poses security problems for enterprises and governments regarding data sovereignty, migration challenges, and legislation. The document then covers various cloud service and deployment models, focusing on hybrid cloud which combines on-site private clouds with outsourced and public cloud options. Several hybrid cloud scenarios are proposed to separate data by confidentiality level. Finally, key security challenges are listed, such as multi-tenancy, security perimeters, integration issues, and the human factor.