Explanation

Amazon Macie is the correct answer because:

• Amazon Macie is specifically designed for data security and sensitive data discovery in AWS
• It uses machine learning and pattern matching to automatically discover, classify, and protect sensitive data
• Macie can continuously monitor S3 buckets for personally identifiable information (PII) and other sensitive data
• It provides immediate alerts when vulnerabilities or unauthorized access is detected
• Macie helps organizations meet compliance requirements for data protection

Why the other options are incorrect:

• Amazon GuardDuty: A threat detection service that monitors for malicious activity and unauthorized behavior, but not specifically for PII discovery in S3
• Amazon Detective: A security service for investigating security issues by analyzing data from AWS resources, but not for proactive PII monitoring
• AWS Shield: A DDoS protection service that safeguards applications running on AWS, not for data classification and PII monitoring

Amazon Macie is the specialized service specifically built for discovering and protecting sensitive data like PII in S3 buckets.