- A
Create an AWS CloudFormation stack policy to block security groups with SSH open to 0.0.0.0/0.
Why wrong: Stack policies control updates, not creation, and cannot enforce security rules.
- B
Use an AWS Config managed rule to detect security groups with unrestricted SSH access and trigger an automatic remediation.
AWS Config can evaluate security group rules and trigger remediation via Systems Manager Automation.
- C
Implement a service control policy (SCP) to deny the ec2:AuthorizeSecurityGroupIngress action for port 22 from 0.0.0.0/0.
Why wrong: SCPs apply to entire accounts or OUs, but do not block resource creation; they deny API calls but can be bypassed if the user has permissions.
- D
Add an IAM policy to deny the ec2:AuthorizeSecurityGroupIngress action for port 22 from 0.0.0.0/0.
Why wrong: While possible, it requires careful IAM management and does not prevent creation of security groups with open SSH via CloudFormation if the user has full permissions.
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. 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.
A company uses AWS CloudFormation to deploy infrastructure. The security team requires that all security groups restrict SSH access to only the company's VPN public IP address range (203.0.113.0/24). A developer creates a stack that includes a security group with SSH open to 0.0.0.0/0. The stack deploys successfully. Which action should the security team take to prevent this in the future?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use an AWS Config managed rule to detect security groups with unrestricted SSH access and trigger an automatic remediation.
Using AWS CloudFormation Stack Policies allows you to define which stack resources can be updated or deleted, but not to enforce security rules. AWS Config rules can evaluate resources against desired configurations and trigger remediation or notifications. Service control policies (SCPs) are for AWS Organizations and cannot block resource creation at the account level. IAM permissions can prevent users from creating security groups with open SSH, but that requires careful management and does not cover all cases. Option B is the correct answer because an AWS Config managed rule can detect security groups with unrestricted SSH access and trigger an automatic remediation action via AWS Systems Manager Automation.
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.
- ✗
Create an AWS CloudFormation stack policy to block security groups with SSH open to 0.0.0.0/0.
Why it's wrong here
Stack policies control updates, not creation, and cannot enforce security rules.
- ✓
Use an AWS Config managed rule to detect security groups with unrestricted SSH access and trigger an automatic remediation.
Why this is correct
AWS Config can evaluate security group rules and trigger remediation via Systems Manager Automation.
Related concept
Standard ACLs match source addresses.
- ✗
Implement a service control policy (SCP) to deny the ec2:AuthorizeSecurityGroupIngress action for port 22 from 0.0.0.0/0.
Why it's wrong here
SCPs apply to entire accounts or OUs, but do not block resource creation; they deny API calls but can be bypassed if the user has permissions.
- ✗
Add an IAM policy to deny the ec2:AuthorizeSecurityGroupIngress action for port 22 from 0.0.0.0/0.
Why it's wrong here
While possible, it requires careful IAM management and does not prevent creation of security groups with open SSH via CloudFormation if the user has full 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 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.
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Infrastructure Security — This question tests Infrastructure Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Use an AWS Config managed rule to detect security groups with unrestricted SSH access and trigger an automatic remediation. — Using AWS CloudFormation Stack Policies allows you to define which stack resources can be updated or deleted, but not to enforce security rules. AWS Config rules can evaluate resources against desired configurations and trigger remediation or notifications. Service control policies (SCPs) are for AWS Organizations and cannot block resource creation at the account level. IAM permissions can prevent users from creating security groups with open SSH, but that requires careful management and does not cover all cases. Option B is the correct answer because an AWS Config managed rule can detect security groups with unrestricted SSH access and trigger an automatic remediation action via AWS Systems Manager Automation.
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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Last reviewed: Jun 20, 2026
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