The shared responsibility model is the security boundary the customer accepted when they signed the cloud contract. AWS articulates it as security "of" the cloud (provider) versus security "in" the cloud (customer). The provider is responsible for the physical security of the data centre, the host operating system, the hypervisor, the physical network and the foundational services. The customer is responsible for the guest operating system, network and firewall configuration, identity and access management, application security, and data encryption. The exact boundary shifts as you move from IaaS to PaaS to SaaS, and the forensic team must know where it sits for any given service.
Identity and Access Management is the customer's first line of control and the examiner's first source of evidence. IAM in AWS, Azure AD (now Entra ID) and GCP IAM all share the same conceptual pieces: principals (users, groups, roles, service accounts), policies (allow or deny statements against actions and resources), and conditions (IP, time, MFA state). SAML and OIDC federation links the cloud IAM to an enterprise identity provider, typically Okta, Microsoft Entra or Google Workspace. Conditional access (Azure AD term) or context-aware access (Google term) layers risk-based rules on top. For the examiner, the principal-to-action audit trail is what reconstructs the actor in an incident. IAM Access Analyzer and IAM Credential Report are the AWS pieces that surface drift.
Encryption is the second pillar. Encryption at rest is handled by KMS-managed keys: AWS KMS, Azure Key Vault, Google Cloud KMS. The default option is provider-managed keys (the provider holds the master key entirely). BYOK lets the customer supply the master key material that the provider's KMS then wraps. HYOK keeps the master key entirely in customer infrastructure, with the cloud workload calling out to decrypt. For an Indian fintech bound by RBI's IT framework, KMS-managed keys with customer-supplied master material is the typical posture. Encryption in transit is TLS 1.2 or 1.3 between every pair of services, terminated either at the load balancer or end-to-end at the workload.
Network security in the cloud is the third pillar. AWS uses VPC (Virtual Private Cloud) as the network boundary, security groups as the stateful per-instance firewall, NACLs as the stateless subnet-level firewall, and AWS Network Firewall plus AWS WAF for deeper inspection. Azure mirrors this with VNet, NSGs and Azure Firewall. GCP mirrors with VPC and firewall rules. The shared theme is software-defined network policy, applied at the hypervisor by the provider, audited by the customer through the API.