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Question 681 of 1,738

Infrastructure Security →hardMultiple SelectObjective-mapped

Quick Answer

The correct answer is to create a security group for the database servers that allows inbound traffic on TCP port 3306 from the web server security group ID, and to ensure the web server security group allows outbound traffic on port 3306 to the database security group. This works because security groups are stateful—when the web server initiates outbound traffic to the database, the corresponding return traffic is automatically permitted, even without an explicit inbound rule on the web side. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of stateful security groups versus stateless network ACLs, and the principle of least privilege by referencing security group IDs instead of broad CIDR ranges. A common trap is trying to add a separate inbound rule for return traffic on the web security group, which is unnecessary due to statefulness. Memory tip: “Stateful means no return rule needed—just point the destination to the other group’s ID.”

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 is migrating a legacy application to AWS. The application requires two-way communication between the web servers and the database servers using TCP port 3306. The security team wants to follow the principle of least privilege. Which TWO actions should be taken to secure the traffic?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.

Question 1hardmulti select

Full question →

A
Create a security group for the web servers that allows outbound traffic on port 3306 to the database security group.
Security groups are stateful and will allow return traffic automatically.
B
Create a security group for the database servers that allows inbound traffic on port 3306 from the web subnet CIDR.
Why wrong: Using the web security group ID as source is more dynamic and secure than IP CIDR.
C
Place the database servers in a public subnet for easier connectivity.
Why wrong: Databases should be in private subnets, not exposed to the internet.
D
Configure the network ACL for the database subnet to allow inbound traffic on port 3306 from the web subnet CIDR.
Why wrong: NACLs are stateless and require explicit outbound rules; security groups are simpler and stateful.
E
Create a security group for the database servers that allows inbound traffic on port 3306 from the web security group ID.
This ensures only instances in the web security group can connect.

Full breakdown with real-world context →

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

✓

Create a security group for the web servers that allows outbound traffic on port 3306 to the database security group.

Option A is correct because security groups are stateful, so allowing outbound traffic on port 3306 from the web servers to the database security group automatically permits the corresponding return traffic. This adheres to the principle of least privilege by specifying the destination as the database security group ID rather than a broad CIDR range, ensuring only the intended web servers can initiate the connection.

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.

✓
Create a security group for the web servers that allows outbound traffic on port 3306 to the database security group.
Why this is correct
Security groups are stateful and will allow return traffic automatically.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a security group for the database servers that allows inbound traffic on port 3306 from the web subnet CIDR.
Why it's wrong here
Using the web security group ID as source is more dynamic and secure than IP CIDR.
✗
Place the database servers in a public subnet for easier connectivity.
Why it's wrong here
Databases should be in private subnets, not exposed to the internet.
✗
Configure the network ACL for the database subnet to allow inbound traffic on port 3306 from the web subnet CIDR.
Why it's wrong here
NACLs are stateless and require explicit outbound rules; security groups are simpler and stateful.
✓
Create a security group for the database servers that allows inbound traffic on port 3306 from the web security group ID.
Why this is correct
This ensures only instances in the web security group can connect.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse security groups (stateful, instance-level) with network ACLs (stateless, subnet-level) and incorrectly assume that a subnet CIDR-based rule in a security group is equivalent to using a security group ID, when in fact the latter provides stricter least-privilege control by limiting access to only the specific instances in the web security group.

Detailed technical explanation

How to think about this question

Security groups operate at the instance level (ENI) and are stateful, meaning that if you allow outbound traffic to a security group, the return traffic is automatically permitted regardless of inbound rules. In contrast, network ACLs are stateless and apply at the subnet level, requiring separate inbound and outbound rules for each direction. When using security group IDs as a source or destination, AWS resolves the rule dynamically to the private IP addresses of all instances associated with that security group, enabling granular control without hardcoding IPs.

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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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: Create a security group for the web servers that allows outbound traffic on port 3306 to the database security group. — Option A is correct because security groups are stateful, so allowing outbound traffic on port 3306 from the web servers to the database security group automatically permits the corresponding return traffic. This adheres to the principle of least privilege by specifying the destination as the database security group ID rather than a broad CIDR range, ensuring only the intended web servers can initiate the connection.

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.

Are there clue words in this question I should notice?

Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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This SCS-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SCS-C02 exam.