SCS-C02 Threat Detection and Incident Response Practice Question
A company has a serverless application using AWS Lambda functions that process sensitive data. The security team wants to detect potential data exfiltration via DNS queries from the Lambda functions. Which service should be enabled to monitor DNS requests?
⚠ Common exam trap
Candidates often confuse AWS WAF (web application firewall) with DNS-layer filtering, or assume GuardDuty natively monitors DNS queries without realizing it requires Route 53 Resolver DNS Firewall as a prerequisite data source.
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
✓
Amazon Route 53 Resolver DNS Firewall
Amazon Route 53 Resolver DNS Firewall is the correct choice because it provides DNS-layer filtering for outbound DNS queries from VPCs, including those made by Lambda functions. It can log and block DNS requests to known malicious domains, enabling detection of data exfiltration attempts that use DNS tunneling or command-and-control (C2) communication. This service integrates with VPC flow logs and CloudWatch to monitor DNS query patterns specifically.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Amazon Route 53 Resolver DNS Firewall
Why this is correct
Amazon Route 53 Resolver DNS Firewall is the correct answer because it operates at the DNS layer, inspecting outbound DNS queries from a VPC. It can both log full DNS query details (through Resolver query logging) and filter/block malicious or unwanted domains before resolution. This is directly applicable to a serverless Lambda application that needs DNS visibility and control, whereas other services operate at different layers or lack native DNS logging.
- ✗
AWS WAF
Why it's wrong here
AWS WAF is incorrect because it is a web application firewall that inspects HTTP/HTTPS traffic, typically fronting ALB, CloudFront, or API Gateway. It can filter requests based on web rules like SQL injection or cross-site scripting, but it has no ability to parse DNS wire protocol or view DNS queries made by a Lambda function. DNS logging is outside its scope, so it cannot provide the required DNS query logs.
- ✗
Amazon CloudWatch Logs
Why it's wrong here
Amazon CloudWatch Logs is incorrect because it is a log storage, monitoring, and alerting service, not a source of DNS data. Lambda itself does not natively log DNS queries—it only logs invocations, console output, and CloudWatch metrics that you explicitly write. To get DNS query logs into CloudWatch Logs, you must send them from a service like Route 53 Resolver DNS Firewall or Resolver query logging, so CloudWatch Logs alone cannot capture or filter DNS queries.
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AWS GuardDuty
Why it's wrong here
AWS GuardDuty is incorrect because it is a threat detection service that analyzes logs (including DNS logs) to identify anomalies and malicious activity. It does not log DNS queries itself and retains only findings, not full query history. GuardDuty can consume DNS logs from Route 53 Resolver and alert on suspicious domains, but it does not provide a complete record of all DNS queries, so it cannot serve as the logging/filtering solution.
Visual reference
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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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.