The answer is to use an AWS Organizations service control policy (SCP) that denies all actions unless MFA is present. This is the most effective method because an SCP sets a central permission guardrail at the account level, meaning it applies to every IAM user and role within that account, and it cannot be overridden by any IAM policy attached to the user. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding of the difference between identity-based policies and account-level guardrails; a common trap is choosing an IAM policy option, which can be bypassed if a user has a separate allow policy, whereas an SCP enforces the MFA requirement universally. Remember the key distinction: SCPs are deny-by-default guardrails that apply to all principals in the account, while IAM policies are per-user and can be overridden. A helpful memory tip is "SCP = Security Ceiling Policy"—it sets the maximum allowed actions, so if MFA is missing, the ceiling drops to zero.
SCS-C02 Identity and Access Management Practice Question
This SCS-C02 practice question tests your understanding of identity and access management. 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.
A security engineer needs to enforce that all IAM users in an AWS account use multi-factor authentication (MFA) when making API calls. What is the MOST effective way to enforce this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use an AWS Organizations service control policy (SCP) that denies all actions unless MFA is present.
Option C is correct because a service control policy (SCP) can be applied at the account level to deny all actions if MFA is not present. Option A is wrong because it only applies to the root user. Option B is wrong because IAM policies can be attached to users but can be overridden. Option D is wrong because CloudTrail logs do not enforce MFA.
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.
Attach an IAM policy that denies all actions unless MFA is present.
Why it's wrong here
Can be effective but can be bypassed if users have other policies allowing actions.
✓
Use an AWS Organizations service control policy (SCP) that denies all actions unless MFA is present.
Why this is correct
Enforces MFA at the account level, overriding any IAM policies.
Related concept
Standard ACLs match source addresses.
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.
Identity and Access Management — This question tests Identity and Access Management — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Use an AWS Organizations service control policy (SCP) that denies all actions unless MFA is present. — Option C is correct because a service control policy (SCP) can be applied at the account level to deny all actions if MFA is not present. Option A is wrong because it only applies to the root user. Option B is wrong because IAM policies can be attached to users but can be overridden. Option D is wrong because CloudTrail logs do not enforce MFA.
What should I do if I get this SCS-C02 question wrong?
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.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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