Quick Answer
The answer is AWS CloudTrail with CloudWatch alarms. This is correct because CloudTrail captures every S3 API call, including `AccessDenied` errors when an IAM user attempts to access a bucket without proper permissions, and CloudWatch Alarms can monitor those specific log events to trigger real-time unauthorized S3 access alerts. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of detective controls and the integration between CloudTrail and CloudWatch for security monitoring—a common trap is choosing S3 server access logs, which are not real-time and lack the granular API-level detail of CloudTrail. Remember that CloudTrail logs the *who*, *what*, and *when* of every denied attempt, while CloudWatch Alarms provides the *alert*. A helpful memory tip: think "Trail for the fail, Watch for the alert"—CloudTrail trails the failed API calls, and CloudWatch watches for them to sound the alarm.
This SCS-C02 practice question tests your understanding of threat detection and incident response. 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.
A company's security team wants to detect unauthorized S3 bucket access attempts in real time. Which service should they use to generate alerts when an IAM user attempts to access a bucket without proper permissions?
Amazon GuardDuty
Why wrong: GuardDuty can detect, but CloudTrail provides immediate per-request logging.
AWS CloudTrail with CloudWatch alarms
CloudTrail logs every API call; metric filters on error codes trigger alarms in real time.
S3 server access logs
Why wrong: Server access logs are written periodically, not real-time.
AWS Config
Why wrong: Config records resource changes, not API access.
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 with CloudWatch alarms
AWS CloudTrail logs all API calls made to S3, including access denied errors. By creating a CloudWatch alarm on the `S3 AccessDenied` event in CloudTrail logs, the security team can receive real-time alerts when an IAM user attempts to access a bucket without proper permissions. This approach directly captures the unauthorized attempt at the API level, enabling immediate detection.
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 GuardDuty
Why it's wrong here
GuardDuty can detect, but CloudTrail provides immediate per-request logging.
AWS CloudTrail with CloudWatch alarms
Why this is correct
CloudTrail logs every API call; metric filters on error codes trigger alarms in real time.
Related concept
Read the scenario before looking for a memorised answer.
S3 server access logs
Why it's wrong here
Server access logs are written periodically, not real-time.
AWS Config
Why it's wrong here
Config records resource changes, not API access.
Common exam traps
The trap here is that candidates often choose Amazon GuardDuty because it is associated with threat detection, but they overlook that GuardDuty does not provide real-time, per-user unauthorized access alerts for S3; instead, CloudTrail with CloudWatch alarms directly captures the specific API error event needed for this use case.
Detailed technical explanation
CloudTrail delivers events to CloudWatch Logs in near real-time (typically within 15 minutes), and a CloudWatch alarm can be configured to trigger on a metric filter that matches the `AccessDenied` error code in the `errorCode` field of the CloudTrail log entry. This setup allows the security team to receive SNS notifications or trigger Lambda functions for immediate response. A subtle behavior is that CloudTrail must be enabled for S3 data events (not just management events) to capture object-level access attempts, which is a common oversight.
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
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Threat Detection and Incident Response — study guide chapter
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FAQ
Threat Detection and Incident Response — This question tests Threat Detection and Incident Response — Read the scenario before looking for a memorised answer..
The correct answer is: AWS CloudTrail with CloudWatch alarms — AWS CloudTrail logs all API calls made to S3, including access denied errors. By creating a CloudWatch alarm on the `S3 AccessDenied` event in CloudTrail logs, the security team can receive real-time alerts when an IAM user attempts to access a bucket without proper permissions. This approach directly captures the unauthorized attempt at the API level, enabling immediate detection.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This SCS-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 SCS-C02 exam.
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