Develop a script that programmatically checks for NAT gateways in an AWS account, sends an email alert, and terminates the NAT gateway if a NAT gateway is detected. Deploy the script on an Amazon EC2 instance in each account. Use a cron job to run the script every 5 minutes. Log the results of the checks to an Amazon RDS for MySQL database.

Create an AWS Lambda function that programmatically checks for NAT gateways in an AWS account, sends an email alert, and terminates the NAT gateway if a NAT gateway is detected. Deploy the Lambda function to each account by using AWS Serverless Application Model (AWS SAM) templates. Store the results of the checks on an Amazon OpenSearch Service cluster in each account.

Enable Amazon GuardDuty. Create an Amazon EventBridge rule for the Behavior:EC2/NATGatewayCreation GuardDuty finding type. Configure the rule to invoke an AWS Step Functions state machine to send an email alert and terminate a NAT gateway if a NAT gateway is detected. Store the runtime log as a text file in an Amazon S3 bucket.

Create a custom AWS Config rule that checks for NAT gateways in an AWS account. Configure the AWS Config rule to perform an AWS Systems Manager Automation remediation action to send an email alert and terminate the NAT gateway if a NAT gateway is detected. Deploy the AWS Config rule and the Systems Manager runbooks to each account by using AWS CloudFormation StackSets