The answer is that the IAM policy in the external account must allow the action, the resource-based policy in the target account must grant access to the external account, and the principal in the external account must be explicitly authorized. This is correct because cross-account IAM access requires a two-way permission check: the resource-based policy (like an S3 bucket policy) acts as a gatekeeper in the account owning the resource, explicitly listing which external accounts or principals are allowed, while the external account’s own IAM policy must also permit the specific action against that resource. On the AWS Certified Security Specialty SCS-C02 exam, this concept tests your understanding of the “resource-based vs. identity-based policy” distinction, often appearing in scenarios where a user tries to access a resource from another account and fails. A common trap is assuming that an IAM policy alone in the external account is sufficient—it is not without the resource-based policy’s explicit allowance. Memory tip: think “both sides must say yes”—the resource owner’s policy invites you in, and your account’s policy lets you walk through the door.
SCS-C02 Identity and Access Management Practice Question
This SCS-C02 practice question tests your understanding of identity and access management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 THREE factors should be considered when designing IAM policies for cross-account access? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The resource-based policy must allow the external account
Option A is correct because for cross-account access using resource-based policies (e.g., S3 bucket policies, KMS key policies), the resource-based policy must explicitly grant access to the external AWS account. This allows the external account's IAM principals to access the resource, provided the external account's IAM policy also permits the action. Without this allowance in the resource-based policy, the external account cannot access the resource, even if its own IAM policies allow it.
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.
✓
The resource-based policy must allow the external account
Why this is correct
The resource must grant access to the external account.
Related concept
Read the scenario before looking for a memorised answer.
✗
Permission boundaries must be used
Why it's wrong here
Boundaries are optional and can further restrict, but not required.
✓
The AWS account ID must be specified in the policy
Why this is correct
Account IDs are used to identify the trusted account.
Related concept
Read the scenario before looking for a memorised answer.
✓
The IAM policy in the external account must allow the action
Why this is correct
The user/role in the external account needs explicit allow.
Related concept
Read the scenario before looking for a memorised answer.
✗
Service control policies (SCPs) must allow the action
Why it's wrong here
SCPs are for organizations, but not a design factor for cross-account access.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that only one policy (either resource-based or identity-based) is sufficient for cross-account access, but in reality both the resource-based policy and the external account's IAM policy must allow the action.
Detailed technical explanation
How to think about this question
Cross-account access relies on a two-step authorization process: the resource-based policy must grant access to the external account (or its specific principals), and the IAM policy in the external account must allow the action on the resource. This is often implemented using AWS Security Token Service (STS) to assume a role or directly access the resource. A common real-world scenario is an S3 bucket policy that allows an external account to write objects, but the external account's IAM user must also have an IAM policy allowing s3:PutObject on that bucket ARN.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Identity and Access Management — This question tests Identity and Access Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The resource-based policy must allow the external account — Option A is correct because for cross-account access using resource-based policies (e.g., S3 bucket policies, KMS key policies), the resource-based policy must explicitly grant access to the external AWS account. This allows the external account's IAM principals to access the resource, provided the external account's IAM policy also permits the action. Without this allowance in the resource-based policy, the external account cannot access the resource, even if its own IAM policies allow it.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.