The correct answer is C. Edit the existing trail in the Organizations management account and apply it to the organization.

The reason is that this is the simplest and most effective way to ensure that there is at least one trail configured for all existing accounts and for any account that is created in the future.According to the AWS documentation1, “If you have created an organization in AWS Organizations, you can create a trail that logs all events for all AWS accounts in that organization.This is sometimes called an organization trail.” The documentation1also states that “The management account for the organization can edit an existing trail in their account, and apply it to an organization, making it an organization trail. Organization trails log events for the management account and all member accounts in the organization.” Therefore, by editing the existing trail in the management account and applying it to the organization, the security team can ensure that all accounts are sending CloudTrail logs to a centralized S3 logging bucket.

The other options are incorrect because:

A. Create a new trail and configure it to send CloudTrail logs to Amazon S3. Use Amazon EventBridge to send notification if a trail is deleted or stopped. This option is not sufficient to ensure that there is at least one trail configured for all accounts, because it does not prevent users from deleting or stopping the trail in their accounts. Even if EventBridge sends a notification, the security team would have to manually restore or restart the trail, which is not efficient or scalable.

B. Deploy an AWS Lambda function in every account to check if there is an existing trail and create a new trail, if needed. This option is not optimal because it requires deploying and maintaining a Lambda function in every account, which adds complexity and cost. Moreover, it does not prevent users from deleting or stopping the trail after it is created by the Lambda function.

D. Create an SCP to deny the cloudtrail:Delete and cloudtrail:Stop actions. Apply the SCP to all accounts. This option is not sufficient to ensure that there is at least one trail configured for all accounts, because it does not create or apply a trail in the first place. It only prevents users from deleting or stopping an existing trail, but it does not guarantee that a trail exists in every account.