Elastic medium stable kql

AWS S3 Unauthenticated Bucket Access by Rare Source

Identifies AWS CloudTrail events where an unauthenticated source is attempting to access an S3 bucket. This activity may indicate a misconfigured S3 bucket policy that allows public access to the bucket, potentially exposing sensitive data to unauthorized users. Adversaries can specify --no-sign-request in the AWS CLI to retrieve objects from an S3 bucket without authentication. This is a New Terms rule, which means it will trigger for each unique combination of the source.address and targeted bucket name that has not been seen making this API request.

View Source

Detection Logic

data_stream.dataset: "aws.cloudtrail"
    and event.provider: "s3.amazonaws.com"
    and event.action: (
        "GetObject" or
        "PutObject" or
        "ListObjects" or
        "DeleteObject" or
        "ListBucket")
    and event.outcome: "success"
    and aws.cloudtrail.user_identity.type: ("AWSAccount" or "Unknown")
    and cloud.account.id: "anonymous"

Field Validations

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