Quick Answer
The answer is Amazon Inspector, VPC Flow Logs, and GuardDuty. Amazon Inspector continuously scans EC2 instances for software vulnerabilities and unintended network exposure, while VPC Flow Logs capture metadata about all IP traffic to and from network interfaces, enabling you to spot anomalous patterns like unexpected outbound connections to known malicious IPs or data exfiltration attempts. GuardDuty uses machine learning and threat intelligence to analyze VPC Flow Logs, DNS logs, and CloudTrail events, identifying suspicious behavior such as cryptocurrency mining or credential abuse. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding of detective controls versus preventive ones; a common trap is confusing AWS Config (which is for compliance auditing) with these real-time detection services. Remember the mnemonic “I V G” (Inspector, VPC Flow Logs, GuardDuty) to recall the three core services for detecting compromised EC2 instances.
This SCS-C02 practice question tests your understanding of threat detection and incident response. 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 AWS services can be used to detect potentially compromised EC2 instances? (Choose 3.)
AWS WAF
Why wrong: WAF protects web applications, not EC2 instances directly.
VPC Flow Logs
Flow Logs can reveal unusual network traffic indicating compromise.
AWS Shield
Why wrong: Shield protects against DDoS attacks.
Amazon GuardDuty
GuardDuty uses threat intelligence to detect compromise.
Amazon Inspector
Inspector assesses instances for vulnerabilities that could lead to compromise.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VPC Flow Logs
VPC Flow Logs capture IP traffic metadata (source/destination IP, ports, protocol, packet/byte counts) for network interfaces in a VPC. By analyzing flow logs for anomalous patterns—such as unexpected outbound connections to known malicious IPs, port scanning, or data exfiltration attempts—you can detect potentially compromised EC2 instances. This makes VPC Flow Logs a key detective control for threat detection.
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.
AWS WAF
Why it's wrong here
WAF protects web applications, not EC2 instances directly.
VPC Flow Logs
Why this is correct
Flow Logs can reveal unusual network traffic indicating compromise.
Related concept
Read the scenario before looking for a memorised answer.
AWS Shield
Why it's wrong here
Shield protects against DDoS attacks.
Amazon GuardDuty
Why this is correct
GuardDuty uses threat intelligence to detect compromise.
Related concept
Read the scenario before looking for a memorised answer.
Amazon Inspector
Why this is correct
Inspector assesses instances for vulnerabilities that could lead to compromise.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse AWS WAF (a web-layer filter) or AWS Shield (a DDoS mitigator) with detective services, when the question specifically asks for services that *detect* compromised instances—not prevent attacks or filter traffic.
Detailed technical explanation
VPC Flow Logs publish logs to Amazon CloudWatch Logs or Amazon S3, where you can use services like Amazon Athena or third-party SIEMs to query for suspicious traffic patterns—such as connections to known C2 servers (e.g., via threat intelligence feeds) or unusual port/protocol combinations (e.g., outbound SSH from a web server). The logs include the `tcp-flags` field (e.g., SYN, RST, FIN) which can help identify incomplete handshakes indicative of scanning activity. In a real-world scenario, a spike in outbound traffic to a foreign IP on port 445 (SMB) from an instance that normally only serves HTTP could indicate a ransomware compromise.
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
Threat Detection and Incident Response — This question tests Threat Detection and Incident Response — Read the scenario before looking for a memorised answer..
The correct answer is: VPC Flow Logs — VPC Flow Logs capture IP traffic metadata (source/destination IP, ports, protocol, packet/byte counts) for network interfaces in a VPC. By analyzing flow logs for anomalous patterns—such as unexpected outbound connections to known malicious IPs, port scanning, or data exfiltration attempts—you can detect potentially compromised EC2 instances. This makes VPC Flow Logs a key detective control for threat detection.
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 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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