The AWS S3 Unknown Requester detection rule is designed to identify access attempts to sensitive S3 buckets that are made by unrecognized or unexpected principal entities. It requires log data from AWS S3 server access logs to verify whether the correct Identity and Access Management (IAM) entities are attempting to access sensitive data stored in S3 buckets. The rule captures details such as the requester, operation type, HTTP status, and various other request metadata to enable thorough investigation of any anomalies. It flags unexpected access as a potential security concern, allowing organizations to enhance their cloud security posture by monitoring and analyzing access patterns.