Final answer:
IAM policies in cloud services follow a 'deny overrides' logic, meaning higher-level policies with explicit deny statements will override any allow permissions granted by lower-level policies. Without an explicit deny, permissions are generally cumulative. Understanding the policy hierarchy is crucial for proper access management.
Step-by-step explanation:
When it comes to Identity and Access Management (IAM) policies in cloud services, it is important to understand the concept of policy evaluation logic. Typically, IAM policies applied at a higher level in the resource hierarchy do not inherently remove access granted at lower levels. Instead, these policies are generally evaluated with a logical 'deny overrides' approach. This means that if any policy explicitly denies a certain action, then that denial will take precedence over any allow statements present in other policies that apply to the same resource and action.
In practical terms, if a lower-level policy grants access to a particular resource, but a higher-level policy explicitly denies that same access, the deny statement will take precedence, effectively removing the granted access. This type of policy evaluation is designed to ensure that no accidental permissions are granted that might contradict an organization's broader security guidelines and requirements.
However, without an explicit deny, permissions granted at a lower level are typically cumulative with permissions granted at higher levels. It is therefore essential to thoroughly understand the hierarchical structure of policies within the specific cloud service provider you are using to manage access properly.