Quick Answer
The correct answer includes AWS Network Firewall, Security Groups, and Network ACLs, as these three services work together to protect a VPC from malicious traffic at different layers of the network stack. AWS Network Firewall provides stateful, application-layer inspection and threat detection across VPC boundaries, while Security Groups act as instance-level, stateful firewalls that implicitly deny all traffic unless explicitly allowed. Network ACLs (NACLs) are stateless, subnet-level firewalls that filter traffic based on rules evaluating source/destination IP, protocol, and port, offering an additional layer of defense by explicitly allowing or denying inbound and outbound traffic at the subnet boundary. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this question tests your understanding of defense-in-depth within a VPC—a common trap is confusing the stateless nature of NACLs with the stateful behavior of Security Groups. A helpful memory tip: think of Security Groups as "smart doorbells" that remember who knocked, NACLs as "bouncers with a checklist" that check every packet fresh, and AWS Network Firewall as the "full security team" scanning for hidden threats.
This DOP-C02 practice question tests your understanding of security and compliance. 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.
Which THREE services can be used to protect a VPC from malicious traffic? (Choose 3.)
Network ACLs
NACLs provide stateless firewall rules at the subnet level.
Security Groups
Security groups act as virtual firewalls for instances.
AWS Shield
Why wrong: Shield is for DDoS protection, not general traffic filtering.
Amazon Route 53 Resolver
Why wrong: Resolver is for DNS resolution, not traffic protection.
AWS Network Firewall
Network Firewall provides stateful inspection and filtering.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Network ACLs
Network ACLs (NACLs) are stateless, subnet-level firewalls that filter traffic based on rules evaluating source/destination IP, protocol, and port. They provide an additional layer of defense by explicitly allowing or denying inbound and outbound traffic at the subnet boundary, making them a correct choice for protecting a VPC from malicious traffic.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Network ACLs
Why this is correct
NACLs provide stateless firewall rules at the subnet level.
Related concept
Read the scenario before looking for a memorised answer.
Security Groups
Why this is correct
Security groups act as virtual firewalls for instances.
Related concept
Read the scenario before looking for a memorised answer.
AWS Shield
Why it's wrong here
Shield is for DDoS protection, not general traffic filtering.
Amazon Route 53 Resolver
Why it's wrong here
Resolver is for DNS resolution, not traffic protection.
AWS Network Firewall
Why this is correct
Network Firewall provides stateful inspection and filtering.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse AWS Shield (a DDoS protection service) with a VPC-level firewall, not realizing it operates at the edge/global layer and does not filter traffic within the VPC itself.
Detailed technical explanation
Network ACLs support numbered rules (1–32766) evaluated in ascending order, with an implicit deny-all at the end, and are stateless, meaning return traffic must be explicitly allowed by a separate outbound rule. Security Groups are stateful, instance-level firewalls that automatically allow return traffic for permitted inbound flows, and they support allow rules only (no explicit deny). AWS Network Firewall provides deep packet inspection, stateful rule groups, and intrusion prevention (IPS) capabilities, integrating with AWS Firewall Manager for centralized policy management across accounts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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Security and Compliance — study guide chapter
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FAQ
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
The correct answer is: Network ACLs — Network ACLs (NACLs) are stateless, subnet-level firewalls that filter traffic based on rules evaluating source/destination IP, protocol, and port. They provide an additional layer of defense by explicitly allowing or denying inbound and outbound traffic at the subnet boundary, making them a correct choice for protecting a VPC from malicious traffic.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This DOP-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 DOP-C02 exam.
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