An Adaptive Security Architecture for Multi-Tenant Cloud Systems Serving Nigerian Financial Institutions

Multi-tenant cloud systems serving Nigerian financial institutions must simultaneously satisfy competing security requirements from multiple banking clients, varying CBN regulatory mandates, and evolving threat landscapes, creating an architectural complexity that static security designs cannot sustainably address. This dissertation develops an adaptive security architecture theory for multi-tenant cloud systems serving Nigerian financial institutions, contributing original architectural theory and validated design artefacts to cloud security engineering research. A design science research methodology is employed across four artefact development cycles, each yielding a refined architectural design and empirical evaluation. Phase one analyses the security architecture requirements of five Nigerian cloud-based core banking system providers serving a combined total of 28 financial institutions, through 30 architectural interviews and security audit documentation review. Phase two develops the Adaptive Multi-Tenant Financial Security Architecture (AMTFSA), incorporating policy-as-code tenant isolation, dynamic access control policy adjustment triggered by behavioural anomaly detection, and a regulatory compliance automation engine mapped to CBN and NDPR requirements. Phase three implements an AMTFSA prototype on a simulated multi-tenant banking environment hosted on AWS, evaluating isolation effectiveness under 12 simulated tenant compromise scenarios, policy adaptation response time, and compliance audit report generation accuracy. Phase four conducts expert evaluation with 10 cloud security architects from Nigerian financial institutions and two international academic peer reviewers. AMTFSA successfully contains all 12 simulated tenant compromise attempts and generates compliant audit reports with 97 percent field accuracy. Keywords: adaptive security architecture, multi-tenant cloud, Nigerian banks, CBN compliance, cloud security