This SCS-C02 practice question tests your understanding of data protection. 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.
Network Topology
Refer to the exhibit. A security engineer is troubleshooting a decryption failure. The command uses the AWS CLI to decrypt a file. The decryption fails with an 'AccessDeniedException' error. The IAM user has the following policy attached:
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The KMS key policy does not grant the IAM user decrypt permission
Option C is correct because the KMS key policy must explicitly allow the IAM user to decrypt. Even if IAM allows, the key policy can deny. Option A is wrong because the command uses the default KMS key if not specified, but the key policy might not allow the user. Option B is wrong because the IAM policy grants decrypt on all keys. Option D is wrong because the file contains the ciphertext, not the key ID.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 KMS key policy does not grant the IAM user decrypt permission
Why this is correct
Key policies can restrict access even if IAM allows.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The IAM user does not have permission to call kms:Decrypt on the specific key
Why it's wrong here
The IAM policy allows Decrypt on all keys.
✗
The ciphertext blob is not valid
Why it's wrong here
An invalid ciphertext would produce a different error.
✗
The IAM user is not authorized to use the AWS CLI
Why it's wrong here
The error is AccessDenied, not authorization to use CLI.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
Data Protection — This question tests Data Protection — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The KMS key policy does not grant the IAM user decrypt permission — Option C is correct because the KMS key policy must explicitly allow the IAM user to decrypt. Even if IAM allows, the key policy can deny. Option A is wrong because the command uses the default KMS key if not specified, but the key policy might not allow the user. Option B is wrong because the IAM policy grants decrypt on all keys. Option D is wrong because the file contains the ciphertext, not the key ID.
What should I do if I get this SCS-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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