Quick Answer
The answer is AWS CloudTrail because it is the only service that records detailed API activity for S3, including the specific PutBucketPolicy or PutBucketAcl calls that change a bucket’s access control. CloudTrail captures the identity of the user, role, or service that made the request, along with the source IP and timestamp, enabling you to find who made an S3 bucket public by searching the event history for policy modifications. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this question tests your understanding of auditing and governance—a common trap is confusing CloudTrail with AWS Config, which records configuration changes but not the identity behind them, or with CloudWatch, which only monitors metrics and alarms. GuardDuty is also a distractor because it detects threats like suspicious access but does not log API calls. Memory tip: think “Trail of evidence”—CloudTrail leaves a trail of who did what, when, and how, making it the go-to for forensic identity tracing.
This DOP-C02 practice question tests your understanding of incident and event response. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A DevOps engineer receives an alert that an Amazon S3 bucket has become publicly accessible. The engineer needs to identify who made the bucket public. Which AWS service should the engineer use to find the API call that changed the bucket policy?
Amazon CloudWatch Logs
Why wrong: CloudWatch Logs are for application logs, not API calls.
AWS CloudTrail
CloudTrail records API calls with identity.
AWS Config
Why wrong: Config records configuration changes but not who made them.
Amazon GuardDuty
Why wrong: GuardDuty detects malicious activity but doesn't log API calls.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
AWS CloudTrail
Option B is correct because CloudTrail records all S3 API calls, including bucket policy changes. Option A is wrong because CloudWatch monitors metrics. Option C is wrong because Config records configuration changes but not the identity. Option D is wrong because GuardDuty detects threats but doesn't log API calls.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Amazon CloudWatch Logs
Why it's wrong here
CloudWatch Logs are for application logs, not API calls.
AWS CloudTrail
Why this is correct
CloudTrail records API calls with identity.
Related concept
Read the scenario before looking for a memorised answer.
AWS Config
Why it's wrong here
Config records configuration changes but not who made them.
Amazon GuardDuty
Why it's wrong here
GuardDuty detects malicious activity but doesn't log API calls.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Incident and Event Response — study guide chapter
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FAQ
Incident and Event Response — This question tests Incident and Event Response — Read the scenario before looking for a memorised answer..
The correct answer is: AWS CloudTrail — Option B is correct because CloudTrail records all S3 API calls, including bucket policy changes. Option A is wrong because CloudWatch monitors metrics. Option C is wrong because Config records configuration changes but not the identity. Option D is wrong because GuardDuty detects threats but doesn't log API calls.
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 20, 2026
This DOP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DOP-C02 exam.
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