The answer is that the EC2 instance is not managed by AWS Systems Manager. This is the most likely reason for Amazon Inspector not finding vulnerabilities because Inspector relies entirely on the SSM Agent to collect telemetry and perform assessments; if the instance is not properly registered with Systems Manager, the agent cannot communicate with the Inspector service, resulting in no findings regardless of the instance’s actual security posture. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding of the dependency chain between Inspector and Systems Manager, often appearing as a trap where candidates mistakenly blame missing IAM roles or security group rules. A common memory tip is to remember that Inspector needs a “manager” — if the instance isn’t managed by SSM, Inspector is effectively blind.
ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 is troubleshooting an issue where Amazon Inspector is not finding any vulnerabilities in an EC2 instance. The instance has the AWS Systems Manager Agent (SSM Agent) installed and is managed by AWS Systems Manager. What is the most likely reason for Inspector not reporting findings?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The EC2 instance is not managed by AWS Systems Manager.
Inspector requires the SSM Agent to be installed and the instance to be properly registered with Systems Manager. If the instance is not managed by Systems Manager, Inspector cannot perform assessments. Missing IAM role, Security Groups, or Subnet would not prevent Inspector from running; they affect other aspects.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The EC2 instance does not have an IAM role that allows Inspector to scan it.
Why it's wrong here
Inspector uses the SSM Agent, not the instance role directly.
✗
The EC2 instance is in a private subnet without a NAT gateway.
Why it's wrong here
SSM can work with VPC endpoints; missing NATgateway is not the most likely cause.
✗
The EC2 instance's security group blocks outbound traffic to the Inspector service.
Why it's wrong here
Inspector uses SSM, which requires outbound connectivity to Systems Manager endpoints, not directly to Inspector.
✓
The EC2 instance is not managed by AWS Systems Manager.
Why this is correct
Inspector requires SSM Agent and instance managed by Systems Manager to perform assessments.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The EC2 instance is not managed by AWS Systems Manager. — Inspector requires the SSM Agent to be installed and the instance to be properly registered with Systems Manager. If the instance is not managed by Systems Manager, Inspector cannot perform assessments. Missing IAM role, Security Groups, or Subnet would not prevent Inspector from running; they affect other aspects.
What should I do if I get this ANS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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