The correct answer is to create a custom IAM role with only the required actions on specific resources. This approach directly implements the principle of least privilege by granting AWS Lambda permissions to S3 and DynamoDB only for the exact actions needed—such as s3:GetObject on a particular bucket and dynamodb:PutItem on a specific table—rather than using broad managed policies like AmazonS3FullAccess. On the Certified Cloud Security Professional (CCSP) exam, this scenario tests your understanding of IAM execution roles and resource-based policies in serverless architectures, often appearing as a trap where candidates choose pre-built policies for convenience. A common mistake is selecting a role with wildcard resources or actions, which violates least privilege and expands the attack surface. Remember the memory tip: “Specific bucket, specific action, specific table—least privilege is the only fable.”
CCSP Cloud Application Security Practice Question
This CCSP practice question tests your understanding of cloud application security. 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 company is implementing a serverless application using AWS Lambda. The function processes S3 events and writes to a DynamoDB table. Which of the following is the MOST secure way to grant the necessary permissions?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a custom IAM role with only the required actions on specific resources
Option D is correct because AWS Lambda functions require an IAM role (execution role) to access other AWS services. By creating a custom IAM role with only the required actions (e.g., s3:GetObject for the specific S3 bucket and dynamodb:PutItem for the specific DynamoDB table), you adhere to the principle of least privilege, minimizing the attack surface and ensuring secure, auditable access.
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.
✗
Use resource-based policies on the Lambda function
Why it's wrong here
Resource-based policies on Lambda are for invocation permissions, not for the function's own access.
✗
Attach a managed policy that grants full access to S3 and DynamoDB
Why it's wrong here
Full access violates least privilege.
✗
Use the root user credentials of the AWS account
Why it's wrong here
Root user should never be used for programmatic access.
✓
Create a custom IAM role with only the required actions on specific resources
Why this is correct
Least privilege with scoped actions and resources.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that resource-based policies on the Lambda function can grant the function permissions to other services, when in fact they only control invocation permissions, not the function's outbound access to resources like S3 or DynamoDB.
Detailed technical explanation
How to think about this question
Under the hood, the Lambda execution role is assumed via AWS Security Token Service (STS) when the function runs, providing temporary credentials that are automatically rotated. The IAM policy attached to this role must explicitly allow actions like s3:GetObject and dynamodb:PutItem on ARNs with specific resource constraints (e.g., "arn:aws:s3:::my-bucket/*" and "arn:aws:dynamodb:us-east-1:123456789012:table/MyTable"). A real-world scenario where this matters is when a compromised Lambda function with overly broad permissions could exfiltrate data from other S3 buckets or corrupt unrelated DynamoDB tables, leading to a data breach.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
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.
Cloud Application Security — This question tests Cloud Application Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a custom IAM role with only the required actions on specific resources — Option D is correct because AWS Lambda functions require an IAM role (execution role) to access other AWS services. By creating a custom IAM role with only the required actions (e.g., s3:GetObject for the specific S3 bucket and dynamodb:PutItem for the specific DynamoDB table), you adhere to the principle of least privilege, minimizing the attack surface and ensuring secure, auditable access.
What should I do if I get this CCSP 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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This CCSP practice question is part of Courseiva's free ISC2 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 CCSP exam.
Question Discussion
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