This SCS-C02 practice question tests your understanding of security logging and monitoring. 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 security engineer wants to capture all DNS queries made by EC2 instances to detect potential data exfiltration. Which AWS service should be used to log the DNS requests?
Use Route 53 Resolver DNS Firewall with query logging
DNS Firewall can log DNS queries for VPCs.
Use Amazon GuardDuty
Why wrong: GuardDuty analyzes logs but does not log DNS queries itself.
Enable VPC Flow Logs
Why wrong: VPC Flow Logs capture IP traffic metadata, not DNS queries.
Enable AWS CloudTrail
Why wrong: CloudTrail logs API calls, not DNS queries.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use Route 53 Resolver DNS Firewall with query logging
Route 53 Resolver DNS Firewall with query logging is the correct choice because it is specifically designed to log all DNS queries made by EC2 instances that use the Route 53 Resolver. This service captures the domain names being queried, the source IP, and the response, enabling detection of DNS-based data exfiltration (e.g., DNS tunneling). It integrates directly with the VPC's DNS resolver, ensuring all outbound DNS traffic from EC2 instances is logged without additional agents.
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.
Use Route 53 Resolver DNS Firewall with query logging
Use Amazon GuardDuty
Why it's wrong here
GuardDuty analyzes logs but does not log DNS queries itself.
Enable VPC Flow Logs
Why it's wrong here
VPC Flow Logs capture IP traffic metadata, not DNS queries.
Enable AWS CloudTrail
Why it's wrong here
CloudTrail logs API calls, not DNS queries.
Common exam traps
The trap here is that candidates often confuse VPC Flow Logs (which show IP-level metadata) with DNS query logs, not realizing that DNS exfiltration requires the actual domain names being queried, which only DNS-specific logging provides.
Detailed technical explanation
Route 53 Resolver DNS Firewall query logging works by sending logs to Amazon S3, CloudWatch Logs, or Kinesis Data Firehose, and each log entry includes fields like `srcaddr`, `domain_name`, `query_type`, and `response_code`. DNS tunneling exfiltration often uses TXT or CNAME records to encode data; query logging captures these patterns, allowing security teams to detect anomalies like high-frequency queries to suspicious domains. The service supports custom domain lists and can block or allow queries based on rules, but logging alone is sufficient for detection.
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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FAQ
Security Logging and Monitoring — This question tests Security Logging and Monitoring — Read the scenario before looking for a memorised answer..
The correct answer is: Use Route 53 Resolver DNS Firewall with query logging — Route 53 Resolver DNS Firewall with query logging is the correct choice because it is specifically designed to log all DNS queries made by EC2 instances that use the Route 53 Resolver. This service captures the domain names being queried, the source IP, and the response, enabling detection of DNS-based data exfiltration (e.g., DNS tunneling). It integrates directly with the VPC's DNS resolver, ensuring all outbound DNS traffic from EC2 instances is logged without additional agents.
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 11, 2026
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.
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