The answer is to modify the KMS key policy to allow only specific IAM roles to use kms:Decrypt. This is correct because a KMS key policy acts as the primary access control for a customer master key, explicitly granting or denying permissions to principals like IAM roles, and it can be scoped to restrict the decrypt action without affecting other operations. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding that KMS key policies are resource-based and can directly limit decryption to specific roles, unlike instance profiles or SCPs which lack this granularity for individual keys. A common trap is confusing SCPs with key policies—SCPs set organization-wide guardrails but cannot target a single role for a specific key action. Memory tip: "Key policy is the key to decrypt control"—remember that for KMS, the key policy is the first line of defense for restricting who can unlock your encrypted data.
SOA-C02 Security and Compliance Practice Question
This SOA-C02 practice question tests your understanding of security and compliance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 uses AWS KMS to encrypt EBS volumes attached to EC2 instances. The security team wants to ensure that only specific IAM roles can decrypt the volumes. Which configuration meets this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Modify the KMS key policy to allow only specific IAM roles to use kms:Decrypt.
Option D is correct because a key policy in KMS can define which IAM roles can use the key for decryption. Option A is wrong because instance profiles do not control decrypt permissions. Option B is wrong because bucket policies are for S3, not EBS. Option C is wrong because SCPs can restrict but are not granular for specific roles.
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.
✗
Use a service control policy to deny kms:Decrypt for all users.
Why it's wrong here
SCPs apply to all principals in the account, not specific roles.
✗
Apply a bucket policy on the EBS snapshot bucket.
Why it's wrong here
Bucket policies are not applicable to EBS volumes.
✓
Modify the KMS key policy to allow only specific IAM roles to use kms:Decrypt.
Why this is correct
KMS key policies can restrict decryption to specific IAM roles.
Related concept
Standard ACLs match source addresses.
✗
Attach an instance profile with a policy that denies ec2:DetachVolume.
Why it's wrong here
This does not control decryption permissions.
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 SOA-C02 ACL questions on filtering logic and placement.
Security and Compliance — This question tests Security and Compliance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Modify the KMS key policy to allow only specific IAM roles to use kms:Decrypt. — Option D is correct because a key policy in KMS can define which IAM roles can use the key for decryption. Option A is wrong because instance profiles do not control decrypt permissions. Option B is wrong because bucket policies are for S3, not EBS. Option C is wrong because SCPs can restrict but are not granular for specific roles.
What should I do if I get this SOA-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 SOA-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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