The correct answer is to export the existing logs to S3, encrypt them with the KMS key, and re-import them into a new log group. This is necessary because CloudWatch Logs applies encryption at rest only to new log events written after encryption is enabled on a log group; it cannot retroactively encrypt existing log data. The underlying technical limitation is that CloudWatch Logs uses a server-side encryption mechanism that is applied at the time of ingestion, not as a batch operation on stored data. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding of the immutable nature of CloudWatch Logs encryption and the distinction between encrypting data in transit versus at rest. A common trap is assuming you can simply toggle encryption on an existing log group or re-encrypt in place, but neither is supported. Memory tip: think of CloudWatch Logs encryption as a "new tenant only" policy—once the data is already moved in, you must evict it (export), secure it (encrypt in S3), and then move it into a new apartment (new log group).
SCS-C02 Security Logging and Monitoring Practice Question
This SCS-C02 practice question tests your understanding of security logging and monitoring. 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 is using Amazon CloudWatch Logs to centralize application logs from EC2 instances. The security team wants to encrypt the log data at rest using a customer-managed KMS key. After enabling encryption on the log group, they notice that new log events are being encrypted, but existing log events are not encrypted. What should the team do to encrypt the existing log events?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Export the existing logs to S3, encrypt them with the KMS key, and re-import them into a new log group.
Option C is correct because CloudWatch Logs does not support encrypting existing log events retroactively. The only way to encrypt them is to export them, re-encrypt, and re-import. Option A is wrong because there is no built-in re-encryption. Option B is wrong because you cannot change the KMS key on an existing log group. Option D is wrong because re-encryption is not supported.
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 the AWS CLI to update the log group's encryption configuration to re-encrypt existing data.
Why it's wrong here
No such operation.
✓
Export the existing logs to S3, encrypt them with the KMS key, and re-import them into a new log group.
Why this is correct
Only way to encrypt existing logs.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable KMS automatic key rotation on the customer-managed key to encrypt existing logs.
Why it's wrong here
Rotation does not encrypt existing data.
✗
Change the KMS key to an AWS managed key to automatically encrypt existing logs.
Why it's wrong here
Cannot change key.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which SCS-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Security Logging and Monitoring — This question tests Security Logging and Monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Export the existing logs to S3, encrypt them with the KMS key, and re-import them into a new log group. — Option C is correct because CloudWatch Logs does not support encrypting existing log events retroactively. The only way to encrypt them is to export them, re-encrypt, and re-import. Option A is wrong because there is no built-in re-encryption. Option B is wrong because you cannot change the KMS key on an existing log group. Option D is wrong because re-encryption is not supported.
What should I do if I get this SCS-C02 question wrong?
Identify which SCS-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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This SCS-C02 practice question is part of Courseiva's free Amazon Web Services 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 SCS-C02 exam.
Question Discussion
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