- A
Add a network ACL rule to deny SSH from 0.0.0.0/0.
Why wrong: NACL is different; security group still allows all.
- B
Modify the inbound SSH rule in the security group to source 203.0.113.0/24.
Directly restricts SSH to company IP range.
- C
Add a network ACL rule to allow SSH from 203.0.113.0/24.
Why wrong: NACL alone doesn't change security group; still open.
- D
Remove the inbound SSH rule from the security group.
Why wrong: Removing rule blocks all SSH, not just restrict.
Question 719 of 1,748
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 has a security group that allows inbound SSH from 0.0.0.0/0. The security team wants to restrict access to only the company's public IP range 203.0.113.0/24. What change should be made?
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
✓
Modify the inbound SSH rule in the security group to source 203.0.113.0/24.
Option B is correct because security groups are stateful and act as a virtual firewall for instances. To restrict inbound SSH access from 0.0.0.0/0 to only the company's public IP range, you must modify the existing inbound rule's source CIDR from 0.0.0.0/0 to 203.0.113.0/24. This change directly updates the allowed source IP range, and since security groups evaluate all rules before making a decision, the more specific allowed range will take effect without needing additional rules.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add a network ACL rule to deny SSH from 0.0.0.0/0.
Why it's wrong here
NACL is different; security group still allows all.
- ✓
Modify the inbound SSH rule in the security group to source 203.0.113.0/24.
Why this is correct
Directly restricts SSH to company IP range.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Add a network ACL rule to allow SSH from 203.0.113.0/24.
Why it's wrong here
NACL alone doesn't change security group; still open.
- ✗
Remove the inbound SSH rule from the security group.
Why it's wrong here
Removing rule blocks all SSH, not just restrict.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the stateless behavior of network ACLs with the stateful behavior of security groups, leading them to incorrectly believe that adding a deny rule in a network ACL can override a security group's allow rule for the same traffic.
Detailed technical explanation
How to think about this question
Security groups are stateful, meaning if you allow inbound SSH from a specific source, the corresponding outbound return traffic is automatically allowed regardless of outbound rules. In contrast, network ACLs are stateless and require explicit rules for both inbound and outbound traffic; this distinction is critical when designing defense-in-depth. A common real-world scenario is when an administrator mistakenly adds a network ACL deny rule thinking it will override a security group allow rule, but because security groups are evaluated before network ACLs for inbound traffic (in a VPC), the security group rule still permits the traffic.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Infrastructure Security — This question tests Infrastructure Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Modify the inbound SSH rule in the security group to source 203.0.113.0/24. — Option B is correct because security groups are stateful and act as a virtual firewall for instances. To restrict inbound SSH access from 0.0.0.0/0 to only the company's public IP range, you must modify the existing inbound rule's source CIDR from 0.0.0.0/0 to 203.0.113.0/24. This change directly updates the allowed source IP range, and since security groups evaluate all rules before making a decision, the more specific allowed range will take effect without needing additional rules.
What should I do if I get this SCS-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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