Quick Answer
The answer is Amazon GuardDuty and Amazon Macie. GuardDuty detects unauthorized S3 access by continuously analyzing S3 data events from CloudTrail, using machine learning and threat intelligence to identify anomalies like access from a known malicious IP or anonymous user patterns. Macie complements this by using machine learning and pattern matching to discover sensitive data in S3 buckets and alert on unauthorized access or policy changes that expose that data. On the AWS Certified Security Specialty SCS-C02 exam, this pairing tests your understanding of detective controls: GuardDuty focuses on behavioral threats and suspicious API activity, while Macie focuses on data classification and exposure risks. A common trap is selecting AWS Config or CloudTrail alone—these are logging and compliance tools, not dedicated threat detection services. Memory tip: GuardDuty guards the gate (unusual behavior), Macie minds the data (sensitive content).
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.
Which TWO AWS services can be used to detect unauthorized access to an S3 bucket? (Select TWO.)
AWS WAF
Why wrong: WAF protects web applications, not S3 access.
AWS CloudTrail
Why wrong: CloudTrail logs API calls but does not detect unauthorized access.
Amazon GuardDuty
GuardDuty includes S3 threat detection findings.
Amazon Macie
Macie can detect suspicious access patterns to S3 buckets.
AWS Config
Why wrong: Config tracks resource configuration, not access patterns.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Amazon GuardDuty
Amazon GuardDuty is a threat detection service that continuously monitors for malicious activity and unauthorized behavior across AWS accounts and workloads. It uses machine learning, anomaly detection, and integrated threat intelligence to analyze S3 data events (e.g., GetObject, PutObject) logged via CloudTrail management and data events, identifying suspicious patterns such as unusual access from a known malicious IP address or an anonymous user gaining access to an S3 bucket.
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.
AWS WAF
Why it's wrong here
WAF protects web applications, not S3 access.
AWS CloudTrail
Why it's wrong here
CloudTrail logs API calls but does not detect unauthorized access.
Amazon GuardDuty
Why this is correct
GuardDuty includes S3 threat detection findings.
Related concept
Read the scenario before looking for a memorised answer.
Amazon Macie
Why this is correct
Macie can detect suspicious access patterns to S3 buckets.
Related concept
Read the scenario before looking for a memorised answer.
AWS Config
Why it's wrong here
Config tracks resource configuration, not access patterns.
Common exam traps
The trap here is that candidates often confuse AWS CloudTrail (a logging service) with a detection service, forgetting that CloudTrail only records events and does not analyze or alert on unauthorized access without additional services like GuardDuty or Amazon Detective.
Detailed technical explanation
GuardDuty's S3 threat detection relies on CloudTrail management events (e.g., PutBucketPolicy) and data events (e.g., GetObject, ListBucket) to build a baseline of normal access patterns; it then flags anomalies such as a sudden spike in downloads from a new geographic location or access using temporary credentials from an unusual source IP. Amazon Macie uses machine learning and pattern matching to automatically discover, classify, and protect sensitive data in S3 buckets (e.g., PII, credentials), and it can alert on unauthorized access by detecting when sensitive data is exposed or accessed in an unexpected manner, such as a large number of objects being read by a new IAM role.
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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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: Amazon GuardDuty — Amazon GuardDuty is a threat detection service that continuously monitors for malicious activity and unauthorized behavior across AWS accounts and workloads. It uses machine learning, anomaly detection, and integrated threat intelligence to analyze S3 data events (e.g., GetObject, PutObject) logged via CloudTrail management and data events, identifying suspicious patterns such as unusual access from a known malicious IP address or an anonymous user gaining access to an S3 bucket.
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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