Amazon Detective is the correct service for identifying suspicious activities in AWS accounts using machine learning.

Explanation of services:

• Amazon Detective: Uses machine learning and statistical analysis to analyze log data from AWS CloudTrail, VPC Flow Logs, and other sources to identify suspicious activities and potential security issues
• AWS Shield: A managed DDoS protection service that safeguards web applications running on AWS
• Amazon Macie: A data security service that uses machine learning to discover and protect sensitive data in Amazon S3
• AWS WAF: A web application firewall that helps protect web applications from common web exploits

Amazon Detective is specifically designed to help security teams conduct faster and more efficient security investigations by automatically collecting and analyzing log data to identify the root cause of potential security issues or suspicious activities.