Information Security professionals today have to be able to demonstrate their security strategies within clearly demonstrable frameworks, and show how these are driven by their organization's business priorities, derived from sound risk management assessments.This Open Enterprise Security Architecture (O-ESA) Guide provides a valuable reference resource for practicing security architects and designers explaining the key security issues, terms, principles, components, and concepts underlying security-related decisions that security architects and designers have to make. In doing so it helps in explaining their security architectures and related decision-making processes to their enterprise architecture colleagues.