The correct approach is to create an IAM role in the bucket owner account and use a bucket policy that grants access to that role. This solution achieves least privilege cross-account S3 bucket access by centralizing permissions in the resource-owning account, requiring users from other accounts to first assume the role and obtain temporary credentials via AWS Security Token Service, which automatically enforces time-bound, scoped access. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of the difference between resource-based policies and identity-based policies for cross-account access, with a common trap being to grant broad access to an entire organization or to all authenticated users. Remember that bucket policies are evaluated at the resource level and can include conditions like `aws:SourceArn` or `aws:userId` to further restrict access to only the assumed role. A useful memory tip is "role first, policy second" — always assume a role in the owner account before applying a bucket policy, never attach policies directly to users in external accounts.
SCS-C02 Identity and Access Management Practice Question
This SCS-C02 practice question tests your understanding of identity and access management. 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 security architect is designing a system where an S3 bucket must be accessed by users from multiple AWS accounts. The solution must use the principle of least privilege. Which approach should be used?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create an IAM role in the bucket owner account and use a bucket policy that grants access to the role
The best approach is to use S3 bucket policies with conditions that require the user to assume a specific IAM role in the bucket owner account. Option D is correct because it centralizes permissions and uses temporary credentials. Option A is wrong because it grants list access to all authenticated users. Option B is wrong because resource-based policies (bucket policies) are better for cross-account. Option C is wrong because it allows full access to the whole organization.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Create an IAM role in the bucket owner account and use a bucket policy that grants access to the role
Why this is correct
Users assume the role and get temporary credentials; bucket policy allows the role.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Grant s3:ListBucket and s3:GetObject to all IAM users in the account
Why it's wrong here
Too permissive and not cross-account.
✗
Use an SCP to allow access to the bucket for all accounts in the organization
Why it's wrong here
SCPs are control policies, not for granting direct access.
✗
Use an IAM role in each account with a bucket policy allowing the role
Why it's wrong here
Each account needs a role, but bucket policy still needs to trust those roles.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related SCS-C02 questions on access control and AAA configuration.
Identity and Access Management — This question tests Identity and Access Management — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Create an IAM role in the bucket owner account and use a bucket policy that grants access to the role — The best approach is to use S3 bucket policies with conditions that require the user to assume a specific IAM role in the bucket owner account. Option D is correct because it centralizes permissions and uses temporary credentials. Option A is wrong because it grants list access to all authenticated users. Option B is wrong because resource-based policies (bucket policies) are better for cross-account. Option C is wrong because it allows full access to the whole organization.
What should I do if I get this SCS-C02 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related SCS-C02 questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Authentication checks who the user is.
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