The correct answer is that the policy allows invocation from any Lambda function across all AWS accounts. This is a critical security concern because the resource-based policy uses a wildcard principal (`*`) without any condition keys like `aws:SourceAccount` or `aws:SourceArn` to restrict invocation to the same account. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how Lambda resource-based policies interact with cross-account access, and it commonly appears as a trap where candidates assume the `*` principal is limited to the same account. A key memory tip: always pair a wildcard principal with a source condition key to prevent unintended cross-account invocation—think of it as “wildcard needs a watchdog.”
SCS-C02 Threat Detection and Incident Response Practice Question
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.
Refer to the exhibit. A security engineer is reviewing a resource-based policy attached to an AWS Lambda function. The engineer notices that the policy allows any Lambda function in the account to invoke the function. Which security concern should the engineer address?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy allows invocation from any Lambda function across all AWS accounts.
Option C is correct because the resource-based policy on the Lambda function uses a principal of `*` without any condition key (such as `aws:SourceAccount` or `aws:SourceArn`) to restrict invocation to only the same account. This means any Lambda function in any AWS account can invoke this function, which is a security concern as it allows cross-account invocation without authorization.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 policy grants excessive permissions by allowing all actions.
Why it's wrong here
The Action is limited to lambda:InvokeFunction, not all actions.
✗
The policy does not specify a resource ARN, so it applies to all functions.
Why it's wrong here
The Resource is specified as a specific function ARN.
✓
The policy allows invocation from any Lambda function across all AWS accounts.
Why this is correct
Without a source account condition, any Lambda service principal can invoke.
Related concept
Read the scenario before looking for a memorised answer.
✗
The policy allows the Lambda service to modify the function code.
Why it's wrong here
The Action is only InvokeFunction, not UpdateFunctionCode.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a wildcard principal (`*`) with a wildcard resource (`*`), assuming that `*` in the principal field automatically restricts to the same account, but it actually allows cross-account access unless a condition key is used.
Detailed technical explanation
How to think about this question
Under the hood, Lambda resource-based policies use the IAM policy language, and when the principal is set to `*` without a condition key like `aws:SourceArn` or `aws:SourceAccount`, the policy grants access to any principal in any AWS account. This is a common misconfiguration because the `*` principal alone does not imply account restriction; it must be explicitly scoped. In a real-world scenario, an attacker could create a Lambda function in their own account and invoke this function, potentially triggering unintended actions or data exfiltration.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Threat Detection and Incident Response — This question tests Threat Detection and Incident Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The policy allows invocation from any Lambda function across all AWS accounts. — Option C is correct because the resource-based policy on the Lambda function uses a principal of `*` without any condition key (such as `aws:SourceAccount` or `aws:SourceArn`) to restrict invocation to only the same account. This means any Lambda function in any AWS account can invoke this function, which is a security concern as it allows cross-account invocation without authorization.
What should I do if I get this SCS-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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