The correct answer is that this IAM policy allows S3 uploads with KMS encryption or without any encryption. This works because the first statement grants s3:PutObject only when the encryption header specifies aws:kms, while the second statement uses a Null condition to allow the action when no encryption header is present at all. Together, these two conditions create an effect that permits both encrypted and unencrypted uploads, but explicitly blocks uploads using other encryption types like AES-256. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how IAM policy evaluation logic handles conditional keys and the Null operator, which is a common trap—students often overlook that a missing header is not the same as a denied header. A useful memory tip is to think of the Null condition as a “blank check”: if the encryption field is empty, the policy says “go ahead,” but if it’s filled with anything other than aws:kms, the request is denied.
SCS-C02 Security Logging and Monitoring Practice Question
This SCS-C02 practice question tests your understanding of security logging and monitoring. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Allows uploads with KMS encryption or without encryption.
The policy allows s3:PutObject only if encryption is set to aws:kms OR if no encryption header is provided (Null condition). Option D is correct because the two statements together allow both encrypted and unencrypted uploads. Option A is wrong because the first statement allows only KMS encryption, but the second allows unencrypted. Option B is wrong because the policy does not explicitly deny unencrypted uploads. Option C is wrong because the second statement allows missing encryption header.
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.
✓
Allows uploads with KMS encryption or without encryption.
Why this is correct
Both conditions are covered by the two statements.
Related concept
Standard ACLs match source addresses.
✗
Allows uploads only when encryption is not specified.
Why it's wrong here
The first statement allows KMS encryption uploads.
✗
Denies uploads when encryption is not provided.
Why it's wrong here
The second statement allows uploads when encryption is not specified.
✗
Allows uploads only when using KMS encryption.
Why it's wrong here
The second statement allows uploads without encryption.
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.
Security Logging and Monitoring — This question tests Security Logging and Monitoring — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Allows uploads with KMS encryption or without encryption. — The policy allows s3:PutObject only if encryption is set to aws:kms OR if no encryption header is provided (Null condition). Option D is correct because the two statements together allow both encrypted and unencrypted uploads. Option A is wrong because the first statement allows only KMS encryption, but the second allows unencrypted. Option B is wrong because the policy does not explicitly deny unencrypted uploads. Option C is wrong because the second statement allows missing encryption header.
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.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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