An Amazon S3 public access assessment combines configuration review with controlled tests of actual object access. A private-looking application screen does not establish whether the underlying storage object can be retrieved through another path.
Start by deciding which storage is intentionally public and which contains customer information. Then verify those decisions using synthetic objects, the relevant AWS settings, and the application’s real delivery routes.
What does S3 Block Public Access do?
AWS documents S3 Block Public Access as controls that override permissions capable of allowing public access. Settings can apply at multiple levels, including account, bucket, and access point, and the effective result depends on the applicable controls.
That feature addresses public exposure. It does not replace a review of which authenticated identities may access customer objects. Keep anonymous access, partner access, and application-role access as separate questions.
Which storage paths should be inventoried?
For an illustrative design agency, list the public portfolio bucket, private client-delivery bucket, temporary processing storage, and any CDN distribution in front of them. Record account, region, owner, data purpose, and intended readers for each.
Map a client download from the portal through the delivery service to the object. Identify any access points and any signed-link mechanism. Document a direct storage endpoint separately from a CDN URL so the assessment does not confuse one route with another.
Include older buckets that the application no longer writes to. A retired upload feature may have left files accessible under its former delivery path.
How can you verify anonymous access safely?
Ask the owner to create clearly labeled test objects in the approved locations. Test their known addresses without AWS credentials or application cookies. Avoid guessing object names or enumerating customer data.
Record the exact route, authentication state, response, and marker contents. If a synthetic private object is returned anonymously, that is concrete exposure evidence. If access is denied, record the tested object and route; one denial does not prove that every object, policy exception, or distribution is private.
For an intentionally public portfolio image, a successful anonymous read is expected. Preserve that positive control so the assessment can tell a correct policy from an unavailable environment.
What about authenticated roles and cross-account access?
Use designated test identities for the agency application and an approved partner. Define which synthetic client objects each should read or change. Compare the effective access with that requirement.
In the agency example, the rendering worker may need to read a project’s source files but not every client archive. Review whether its permissions and object selection enforce that separation. A bucket protected from anonymous access can still have overly broad authenticated access.
Retain the relevant policy statements and role assumptions with the observed result. Policy review explains the decision; controlled access testing shows the behavior in the selected case.
What should a storage remediation preserve?
After changing access settings, repeat the private-object rejection, the legitimate client download, and the public portfolio read. Confirm that the intended delivery service still works and that a direct route does not bypass it.
For a Ceron cloud assessment, provide authorized read access to configuration, test identities, and synthetic objects. The report should name the exposed route or excessive permission and explain which retests establish closure.
Presigned URL security addresses temporary links to private objects. Cloud audit log coverage explains how to check whether file access is recorded. The agency scenario is illustrative.
