- A
Condition with sts:ExternalId
Correct. The sts:ExternalId condition key in the bucket policy ensures that the request includes a specific external ID, which the vendor must supply when assuming the role.
- B
Condition with aws:SourceArn
Why wrong: Incorrect. aws:SourceArn is used to restrict requests to a specific resource ARN, not for an external identifier.
- C
Condition with aws:SourceAccount
Why wrong: Incorrect. aws:SourceAccount restricts based on the AWS account ID of the resource, but it does not provide a unique identifier per vendor request.
- D
Principal element with the vendor's AWS account ID
Why wrong: Incorrect. Specifying the principal alone does not enforce a unique identifier. The vendor could misuse the policy from other roles in their account.
DVA-C02 Security Practice Question
This DVA-C02 practice question tests your understanding of security. 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 wants to grant a third-party vendor access to an Amazon S3 bucket in the company's AWS account. The vendor has their own AWS account. The company requires the vendor to include a unique identifier in each request to verify their identity before granting access. Which policy element should the company include in the S3 bucket policy?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Condition with sts:ExternalId
The `sts:ExternalId` condition key is specifically designed for scenarios where a third party (the vendor) needs to access AWS resources in your account, and you want to ensure that the vendor includes a unique identifier in each request. This prevents the confused deputy problem by requiring the vendor to pass the external ID in the `AssumeRole` call or directly in the request to S3 when using role-based access. By including this condition in the bucket policy, the company can verify that the request originates from the intended vendor and not from another entity trying to misuse the permissions.
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.
- ✓
Condition with sts:ExternalId
Why this is correct
Correct. The sts:ExternalId condition key in the bucket policy ensures that the request includes a specific external ID, which the vendor must supply when assuming the role.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Condition with aws:SourceArn
Why it's wrong here
Incorrect. aws:SourceArn is used to restrict requests to a specific resource ARN, not for an external identifier.
- ✗
Condition with aws:SourceAccount
Why it's wrong here
Incorrect. aws:SourceAccount restricts based on the AWS account ID of the resource, but it does not provide a unique identifier per vendor request.
- ✗
Principal element with the vendor's AWS account ID
Why it's wrong here
Incorrect. Specifying the principal alone does not enforce a unique identifier. The vendor could misuse the policy from other roles in their account.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse `aws:SourceArn` or `aws:SourceAccount` with identity verification, but these are used for resource-based policies to restrict based on the source of the request, not for enforcing a unique per-request identifier from a third-party vendor.
Detailed technical explanation
How to think about this question
The `sts:ExternalId` condition is typically used in cross-account role trust policies to prevent the confused deputy problem, where a malicious actor tricks a legitimate service into accessing resources. When applied to an S3 bucket policy, it works by requiring the vendor to include the external ID in the `x-amz-security-token` header (for temporary credentials) or in the `Condition` block of the request, ensuring that only requests with the correct unique identifier are allowed. A real-world scenario is when a SaaS provider needs to access customer S3 buckets; the customer generates a unique external ID per vendor, and the vendor must pass it in every request to prove their identity.
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.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Condition with sts:ExternalId — The `sts:ExternalId` condition key is specifically designed for scenarios where a third party (the vendor) needs to access AWS resources in your account, and you want to ensure that the vendor includes a unique identifier in each request. This prevents the confused deputy problem by requiring the vendor to pass the external ID in the `AssumeRole` call or directly in the request to S3 when using role-based access. By including this condition in the bucket policy, the company can verify that the request originates from the intended vendor and not from another entity trying to misuse the permissions.
What should I do if I get this DVA-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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Last reviewed: Jun 11, 2026
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