A company's web application runs on multiple Amazon EC2 instances behind an Application Load Balancer in a VPC, with an Amazon RDS for MySQL DB instance for data storage. The company needs to automatically detect and respond to suspicious or unexpected behavior in its AWS environment. AWS WAF is already in place. What should a solutions architect implement next to protect against threats?

The correct option leverages Amazon GuardDuty for intelligent threat detection across the AWS environment. GuardDuty continuously monitors for malicious activity and unauthorized behavior. Integrating GuardDuty with Amazon EventBridge allows for automated responses to specific findings. EventBridge can filter for high-severity GuardDuty findings and trigger an AWS Lambda function. This Lambda function can then programmatically update AWS WAF rules, such as blocking suspicious IP addresses or patterns, providing a proactive and automated defense against emerging threats. AWS Firewall Manager is primarily for centralized management of WAF rules, security groups, and other firewall policies across multiple accounts and resources, not for threat detection itself. Amazon Inspector is a vulnerability management service that scans EC2 instances and container images for software vulnerabilities and unintended network exposure, not for real-time threat detection of suspicious activity. Amazon Macie is a data security and privacy service that discovers and protects sensitive data in S3 buckets, not a general threat detection service for the entire AWS environment. Creating a VPC network ACL is a foundational security measure but doesn't provide dynamic threat detection and automated response to suspicious behavior like GuardDuty.