Using CloudTrail to Detect Unauthorized S3 Bucket Access
This SCS-C02 practice question tests your understanding of security logging and monitoring. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Refer to the exhibit. A security engineer finds this S3 bucket policy on a bucket that should be private. What is the most effective way to detect if this bucket was accessed by unauthorized users?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Query AWS CloudTrail for GetObject API calls.
Option B is correct because AWS CloudTrail records all S3 API calls, including GetObject requests, with details such as the source IP address, user identity, and timestamp. Since the bucket policy (not shown in the exhibit but implied to be overly permissive) allows unauthorized access, CloudTrail logs provide the definitive audit trail to identify who accessed the bucket and whether they were authorized. S3 server access logs (Option A) are less effective for real-time detection and lack the granular IAM user context that CloudTrail offers.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Enable S3 server access logs on the bucket.
Why it's wrong here
Server access logs need to be enabled first; they are not historic.
✓
Query AWS CloudTrail for GetObject API calls.
Why this is correct
CloudTrail logs all S3 API calls, including GetObject, and can be queried.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use CloudWatch Logs to search for GetObject events.
Why it's wrong here
CloudWatch Logs does not contain S3 API calls unless configured.
✗
Analyze VPC Flow Logs for traffic to the bucket.
Why it's wrong here
VPC Flow Logs capture network traffic, not S3 API calls.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse S3 server access logs (which log object-level requests) with CloudTrail (which logs API calls with identity context), leading them to choose Option A because it seems more granular, but they miss that CloudTrail is the authoritative source for identifying who made the request and whether they were authorized.
Detailed technical explanation
How to think about this question
CloudTrail records S3 data events (e.g., GetObject, PutObject) only when explicitly enabled via a trail or event data store; by default, only management events are logged. For a private bucket that was accessed by unauthorized users, you would need to have enabled data event logging for the bucket in CloudTrail, which captures the exact IAM user or role, source IP, and request parameters. In contrast, S3 server access logs provide object-level access details but lack the AWS identity context (e.g., user ARN) and are subject to eventual consistency, making them unsuitable for forensic investigation of unauthorized access.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Quick reference
AWS S3 Storage Class Comparison
Storage Class
Min Duration
Retrieval
Use Case
S3 Standard
None
Immediate
Frequently accessed data
S3 Standard-IA
30 days
Immediate
Infrequent access, rapid retrieval
S3 One Zone-IA
30 days
Immediate
Non-critical infrequent data
S3 Intelligent-Tiering
None
Immediate–hours
Unknown or changing access patterns
S3 Glacier Instant
90 days
Milliseconds
Archive with instant retrieval
S3 Glacier Flexible
90 days
Minutes–hours
Archive, flexible retrieval
S3 Glacier Deep Archive
180 days
Hours
Long-term compliance archive
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Logging and Monitoring — This question tests Security Logging and Monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Query AWS CloudTrail for GetObject API calls. — Option B is correct because AWS CloudTrail records all S3 API calls, including GetObject requests, with details such as the source IP address, user identity, and timestamp. Since the bucket policy (not shown in the exhibit but implied to be overly permissive) allows unauthorized access, CloudTrail logs provide the definitive audit trail to identify who accessed the bucket and whether they were authorized. S3 server access logs (Option A) are less effective for real-time detection and lack the granular IAM user context that CloudTrail offers.
What should I do if I get this SCS-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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