Access Control

Access control answers a practical question: may this requester perform this action on this resource in this context? A requester can be a person, application, workload role, or cloud service. Authentication establishes identity; authorization evaluates whether a requested operation is permitted. Successful sign-in does not imply permission to read a database, change a firewall, or view security logs.

Cloud platforms commonly express permissions through policies attached to identities or resources. Roles collect permissions that users or workloads can assume, while attributes such as resource tags, organization membership, source network, or session characteristics can influence decisions. For example, a deployment role might update an application but lack permission to read its production secrets. Temporary role credentials reduce dependence on long-lived access keys, although their permissions and session duration still require careful design.

Least privilege means granting only the actions, resources, and conditions required for a task. In AWS, requests are implicitly denied unless applicable policies allow them, and an applicable explicit deny overrides an allow. Effective authorization can also depend on permissions boundaries, session policies, organization policies, and resource policies. A permissions boundary or service control policy limits possible permissions; it does not grant permissions by itself. Cross-account access often requires both permission for the caller and an appropriate trust or resource policy in the destination account.

Infrastructure location and authorization are separate concerns. An AWS Region is a geographic area containing multiple Availability Zones, which provide separate infrastructure locations for resilient deployments. Edge locations serve functions such as content delivery closer to viewers and are not Availability Zones. IAM is a global service within an AWS partition, while many resources and their permissions reference a particular Region. Deploying across Availability Zones improves availability but does not automatically change access rights. Likewise, selecting a Region does not create a geographic access restriction; enforce such requirements with appropriate policies and service-specific controls.

Access control operates at multiple layers. Network rules determine whether traffic can reach an endpoint, while application and identity policies determine what requests are accepted. A reachable API can still reject an unauthorized request, and a correctly authorized request can fail because routing or firewall rules block connectivity. Public content delivered through an edge location also does not require a publicly accessible origin: a distribution can authorize origin requests while restricting viewers through signed URLs or cookies.

Monitoring pipelines need their own permissions. A Lambda function can execute successfully yet fail to write logs if its execution role lacks the necessary CloudWatch Logs permissions. API Gateway logging requires the appropriate logging configuration and delivery permissions for the API type. CloudFront log delivery requires compatible destination settings and permissions for the selected logging mechanism. Check encryption-key permissions where relevant, destination policies, account and Region selection, and whether the relevant logging feature is enabled before interpreting missing records as an absence of activity.

Health checks illustrate the difference between connectivity and authorization. A health-check request can fail because a firewall blocks the checker, TLS settings are incompatible, or the endpoint requires credentials the checker does not supply. Prefer a narrowly scoped health endpoint that reveals little information rather than weakening authorization for the entire application. Similarly, give log producers permission to write only to intended destinations, and separate log-reading privileges from permissions to delete logs or disable collection.

The main trade-off is precision versus operational complexity. Broad permissions simplify initial setup but increase the damage possible from mistakes or compromised credentials. Highly restrictive policies can break deployments and obscure monitoring failures. Use tested policy changes, access-denied evidence, policy analysis, and periodic permission reviews to refine access. Audit logs provide evidence of activity, but they are not themselves an enforcement mechanism, and an administrator label does not guarantee unrestricted access through every policy layer.