The correct answer is to use a service control policy (SCP) to deny the launch of restricted EC2 instance types and an AWS Config rule to detect and automatically stop noncompliant instances. SCPs operate at the AWS Organizations level, allowing you to centrally block the ec2:RunInstances action for specific instance families across all member accounts, while AWS Config can evaluate running instances against a custom rule and trigger an auto-remediation action, such as stopping or terminating the instance. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding of the layered defense model: SCPs provide preventive control at the account boundary, and Config provides detective and corrective control within the account. A common trap is confusing IAM roles with SCPs—remember that IAM roles cannot restrict resource types across accounts, and CloudTrail only logs, it does not enforce. Memory tip: SCPs say “no” before launch, Config says “stop” after launch.
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. 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 company uses AWS Organizations and wants to restrict the use of specific instance types across all accounts. Which TWO actions should be taken to enforce this restriction?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Apply a Service Control Policy (SCP) that denies ec2:RunInstances with noncompliant instance types.
Options B and D are correct. SCPs can deny actions based on instance type, and AWS Config can detect noncompliant instances. Option A is wrong because IAM roles do not restrict resource types. Option C is wrong because CloudTrail does not enforce. Option E is wrong because VPC does not relate to instance types.
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.
✗
Restrict instance types at the VPC level using network ACLs.
Why it's wrong here
NACLs are network-layer, cannot filter instance types.
✗
Use AWS CloudTrail to monitor instance launches and send alerts.
Why it's wrong here
CloudTrail is detective, not preventive.
✓
Apply a Service Control Policy (SCP) that denies ec2:RunInstances with noncompliant instance types.
Why this is correct
SCPs centrally deny actions across accounts.
Related concept
Standard ACLs match source addresses.
✗
Create an IAM role that denies launch of noncompliant instances.
Why it's wrong here
IAM roles do not enforce resource-level restrictions across accounts.
✓
Use AWS Config rules to detect and automatically stop noncompliant instances.
Why this is correct
Config rules can trigger remediation to stop instances.
Related concept
Standard ACLs match source addresses.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Infrastructure Security — This question tests Infrastructure Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Apply a Service Control Policy (SCP) that denies ec2:RunInstances with noncompliant instance types. — Options B and D are correct. SCPs can deny actions based on instance type, and AWS Config can detect noncompliant instances. Option A is wrong because IAM roles do not restrict resource types. Option C is wrong because CloudTrail does not enforce. Option E is wrong because VPC does not relate to instance types.
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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