SCS-C02 Security Logging and Monitoring Practice Question
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?
⚠ Common exam trap
Watch out — 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.
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 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.
Answer analysis
Option-by-option breakdown
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
Why this is correct
Route 53 Resolver DNS Firewall query logging captures every DNS query that instances resolve through the Amazon-provided VPC resolver, publishing records to CloudWatch Logs, S3, or Kinesis Data Firehose. This satisfies the requirement to log all EC2 DNS requests for exfiltration detection, since instances use that resolver by default.
- ✗
Use Amazon GuardDuty
Why it's wrong here
GuardDuty is a threat-detection service that analyses existing logs and findings; it does not itself capture or store raw DNS query logs for later inspection. It is tempting because it surfaces DNS-based exfiltration findings, and would be correct for alerting on suspicious activity rather than logging queries.
- ✗
Enable VPC Flow Logs
Why it's wrong here
VPC Flow Logs capture IP traffic metadata for network interfaces, including source and destination addresses and ports, but not DNS query names, so exfiltration domains remain invisible. It is tempting because it logs network activity, and would be correct for analysing connection patterns rather than DNS queries.
- ✗
Enable AWS CloudTrail
Why it's wrong here
CloudTrail records AWS API activity and management events, not the DNS queries EC2 instances resolve, so it captures no query names or destinations. It is tempting because it is the default audit-logging service, and would be correct for tracking who called which AWS API.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.