Range Scenario · gauntlet · 30 min
Cloud Misconfiguration: An Exposed S3 Bucket
This cybersecurity training scenario simulates a working incident. A security researcher emails your disclosure inbox: an S3 bucket holding 1.4 million customer PDFs is reachable without authentication. You have one hour before the researcher posts. Identify the misconfig, contain, document.
Scenario briefing
You are the on-call cybersecurity engineer for a SaaS company. At 4:42pm a researcher emails security disclosures with a screenshot showing public listing of an S3 bucket holding customer-uploaded PDFs. The bucket name matches a production naming convention. The researcher gave you 60 minutes before they post on their blog.
You have read access to the AWS account through a federated SSO role with security-auditor permissions. You have approval to invoke the documented break-glass procedure to make changes if the situation warrants it.
This scenario tests whether you can identify cloud misconfiguration root causes, prioritize containment over root cause investigation, and document for both regulatory and engineering audiences.
What you will practice
- Distinguish bucket policy, ACL, and Block Public Access settings
- Pick containment that does not break legitimate downstream consumers
- Map cloud data exposure to MITRE ATT&CK and to GDPR / state breach laws
- Document for engineering, legal, and customer-comms audiences in parallel
How this scenario is scored
The scenario has 6 ordered steps. Most steps are exact-match (a MITRE ATT&CK technique ID, a tool name, or a yes/no decision) or multiple choice. Free-text steps queue for manual review and do not affect the auto-final-score in the MVP.
Each step has a max score of 100 points. Hints deduct points up front, listed before you reveal them. Your final score is the sum across steps. Range Elo updates on completion based on scenario difficulty (Intermediate) and your final score percentage.
Frequently asked questions
What is the difference between S3 bucket policy, ACL, and Block Public Access?
Bucket policy is a JSON document that grants or denies access at the bucket or object level by IAM principal. ACL is a legacy per-object access control list. Block Public Access is an account- and bucket-level setting that overrides both and refuses any configuration that would make the bucket public, even if a policy or ACL would allow it.
Should I make the bucket private immediately or investigate first?
Containment first. A public bucket holding regulated data is an active exposure. Enable Block Public Access at the bucket level, capture the current policy and ACL state for forensics, and only then begin investigation of how the misconfiguration happened. Lost evidence is recoverable from CloudTrail; ongoing exposure is not.
What does the disclosure timeline look like under state breach laws?
Most US state breach notification laws trigger on unauthorized acquisition of personal information, with notification windows ranging from 30 to 90 days. The clock typically starts at discovery. Document discovery time, contained time, and the specific data fields involved so legal can map the exposure against applicable jurisdictions.
Course content is for educational purposes only and does not constitute professional advice. All claims are supported by cited peer-reviewed academic research. DecipherU does not teach or reproduce any proprietary sales methodology. Verify all referenced sources independently.
Get cybersecurity career insights delivered weekly
Join cybersecurity professionals receiving weekly intelligence on threats, job market trends, salary data, and career growth strategies.
By subscribing you agree to our privacy policy. Unsubscribe anytime.