← SCS-C02·Amazon Web Services

Question 40 of 1,748

Management and Security Governance →hardMultiple ChoiceObjective-mapped

MFA Enforcement Not Working for Root Users | AWS Security Specialty

This SCS-C02 practice question tests your understanding of management and security 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 company has a single AWS account with multiple IAM users. The security team wants to enforce that all IAM users must use multi-factor authentication (MFA) to access the AWS Management Console. They attach an IAM policy that denies all actions if the user does not have MFA. However, after attaching the policy, some users report that they are unable to perform any actions even after authenticating with MFA. The policy uses the condition "aws:MultiFactorAuthPresent": "false". The security team verifies that the users have MFA enabled and are using it. What is the most likely cause of this issue?

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.

A
The condition should be "Bool": "aws:MultiFactorAuthPresent": "false" but the policy uses StringLike.
Why wrong: The policy does not need to use Bool; StringLike works for this condition key. This is not the cause.
B
The policy is missing a NotAction element; it should deny all actions except for the ones needed for MFA enrollment.
Why wrong: A NotAction element is not necessary; the policy's intent is to deny all actions when MFA is not present. The issue is that the deny approach is wrong to begin with.
C
The policy is incorrectly written; it should use "Effect": "Allow" and the condition "aws:MultiFactorAuthPresent": "true".
Correct. The policy should use Effect: Allow with the condition, because a Deny without a corresponding Allow results in no permissions. The condition should check that MFA is present to Allow actions.
D
The users are signing in as the root user of the account, not as IAM users.
Why wrong: Incorrect. Root user has full permissions and is not affected by IAM policies. The users are likely IAM users, and the problem is the policy logic.

Full breakdown with real-world context →

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

✓

The policy is incorrectly written; it should use "Effect": "Allow" and the condition "aws:MultiFactorAuthPresent": "true".

The correct approach is to use an Allow policy with the condition that MFA must be present. The Deny policy as written will deny all actions even when MFA is present if there is no other Allow policy granting permissions. Since IAM defaults to implicit deny, a Deny policy is not sufficient to grant access; it only restricts. Therefore, users cannot perform any actions because there is no Allow statement. Option C correctly identifies this.

Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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 condition should be "Bool": "aws:MultiFactorAuthPresent": "false" but the policy uses StringLike.
Why it's wrong here
The policy does not need to use Bool; StringLike works for this condition key. This is not the cause.
✗
The policy is missing a NotAction element; it should deny all actions except for the ones needed for MFA enrollment.
Why it's wrong here
A NotAction element is not necessary; the policy's intent is to deny all actions when MFA is not present. The issue is that the deny approach is wrong to begin with.
✓
The policy is incorrectly written; it should use "Effect": "Allow" and the condition "aws:MultiFactorAuthPresent": "true".
Why this is correct
Correct. The policy should use Effect: Allow with the condition, because a Deny without a corresponding Allow results in no permissions. The condition should check that MFA is present to Allow actions.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The users are signing in as the root user of the account, not as IAM users.
Why it's wrong here
Incorrect. Root user has full permissions and is not affected by IAM policies. The users are likely IAM users, and the problem is the policy logic.

Common exam traps

Common exam trap: ACLs stop at the first match

ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.

Detailed technical explanation

How to think about this question

ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.

KKey Concepts to Remember

Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.

TExam Day Tips

Check inbound versus outbound direction.
Read the ACL from top to bottom.
Look for a broader permit or deny above the intended line.

Key takeaway

ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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 ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.

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FAQ

Questions learners often ask

What does this SCS-C02 question test?

Management and Security Governance — This question tests Management and Security Governance — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: The policy is incorrectly written; it should use "Effect": "Allow" and the condition "aws:MultiFactorAuthPresent": "true". — The correct approach is to use an Allow policy with the condition that MFA must be present. The Deny policy as written will deny all actions even when MFA is present if there is no other Allow policy granting permissions. Since IAM defaults to implicit deny, a Deny policy is not sufficient to grant access; it only restricts. Therefore, users cannot perform any actions because there is no Allow statement. Option C correctly identifies this.

What should I do if I get this SCS-C02 question wrong?

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?

Standard ACLs match source addresses.

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