Detecting AWS Guardduty Findings Automation

Detecting AWS GuardDuty Findings Automation

Overview

Amazon GuardDuty is a threat detection service that continuously monitors AWS accounts for malicious activity and unauthorized behavior. By integrating GuardDuty with Amazon EventBridge and AWS Lambda, security teams achieve automated, real-time responses to threats, reducing mean time to response (MTTR) from hours to seconds. GuardDuty analyzes VPC Flow Logs, CloudTrail management and data events, DNS logs, EKS audit logs, and S3 data events.

When to Use

Trigger phrases:

• "detecting aws guardduty findings automation"

• "Automate AWS GuardDuty threat detection findings processing using EventBridge an"

• When investigating security incidents that require detecting aws guardduty findings automation

• When building detection rules or threat hunting queries for this domain

• When SOC analysts need structured procedures for this analysis type

• When validating security monitoring coverage for related attack techniques

Prerequisites

• AWS account with GuardDuty enabled
• IAM roles for Lambda execution
• EventBridge configured for GuardDuty events
• SNS topic for security notifications
• Security Hub integration (recommended)

Enable GuardDuty

# Enable GuardDuty
aws guardduty create-detector --enable --finding-publishing-frequency FIFTEEN_MINUTES

# Enable additional data sources
aws guardduty update-detector \
  --detector-id DETECTOR_ID \
  --data-sources '{
    "S3Logs": {"Enable": true},
    "Kubernetes": {"AuditLogs": {"Enable": true}},
    "MalwareProtection": {"ScanEc2InstanceWithFindings": {"EbsVolumes": true}},
    "RuntimeMonitoring": {"Enable": true}
  }'

EventBridge Rule Configuration

This section covers eventbridge rule configuration for detecting aws guardduty findings automation.

• Ensure all prerequisites are met before proceeding
• Follow the documented workflow steps in sequence
• Record results and any anomalies encountered during this phase

Rule for high-severity findings

{
  "source": ["aws.guardduty"],
  "detail-type": ["GuardDuty Finding"],
  "detail": {
    "severity": [{"numeric": [">=", 7.0]}]
  }
}

Create EventBridge rule via CLI

aws events put-rule \
  --name "guardduty-high-severity" \
  --event-pattern '{
    "source": ["aws.guardduty"],
    "detail-type": ["GuardDuty Finding"],
    "detail": {
      "severity": [{"numeric": [">=", 7.0]}]
    }
  }'

aws events put-targets \
  --rule "guardduty-high-severity" \
  --targets "Id"="lambda-handler","Arn"="arn:aws:lambda:us-east-1:123456789012:function:guardduty-response"

Lambda Automated Response Functions

This section covers lambda automated response functions for detecting aws guardduty findings automation.

• Ensure all prerequisites are met before proceeding
• Follow the documented workflow steps in sequence
• Record results and any anomalies encountered during this phase

EC2 Instance Isolation

import boto3
import json
import os

ec2 = boto3.client('ec2')
sns = boto3.client('sns')

QUARANTINE_SG = os.environ.get('QUARANTINE_SECURITY_GROUP')
SNS_TOPIC = os.environ.get('SNS_TOPIC_ARN')

def lambda_handler(event, context):
    finding = event['detail']
    finding_type = finding['type']
    severity = finding['severity']
    account_id = finding['accountId']
    region = finding['region']

    # Extract resource information
    resource = finding.get('resource', {})
    resource_type = resource.get('resourceType', '')

    if resource_type == 'Instance':
        instance_id = resource['instanceDetails']['instanceId']
        instance_tags = {t['key']: t['value']
                        for t in resource['instanceDetails'].get('tags', [])}

        # Skip if already quarantined
        if instance_tags.get('SecurityStatus') == 'Quarantined':
            return {'statusCode': 200, 'body': 'Already quarantined'}

        # Get current security groups for forensics
        instance = ec2.describe_instances(InstanceIds=[instance_id])
        current_sgs = [sg['GroupId'] for sg in
                       instance['Reservations'][0]['Instances'][0]['SecurityGroups']]

        # Tag instance with finding info and original SGs
        ec2.create_tags(
            Resources=[instance_id],
            Tags=[
                {'Key': 'SecurityStatus', 'Value': 'Quarantined'},
                {'Key': 'GuardDutyFinding', 'Value': finding_type},
                {'Key': 'OriginalSecurityGroups', 'Value': ','.join(current_sgs)},
                {'Key': 'QuarantineTime', 'Value': finding['updatedAt']}
            ]
        )

        # Move to quarantine security group (blocks all traffic)
        if QUARANTINE_SG:
            ec2.modify_instance_attribute(
                InstanceId=instance_id,
                Groups=[QUARANTINE_SG]
            )

        # Create EBS snapshots for forensics
        volumes = ec2.describe_volumes(
            Filters=[{'Name': 'attachment.instance-id', 'Values': [instance_id]}]
        )
        for vol in volumes['Volumes']:
            ec2.create_snapshot(
                VolumeId=vol['VolumeId'],
                Description=f'GuardDuty forensic snapshot - {finding_type}',
                TagSpecifications=[{
                    'ResourceType': 'snapshot',
                    'Tags': [
                        {'Key': 'Purpose', 'Value': 'ForensicCapture'},
                        {'Key': 'SourceInstance', 'Value': instance_id},
                        {'Key': 'FindingType', 'Value': finding_type}
                    ]
                }]
            )

        # Notify security team
        sns.publish(
            TopicArn=SNS_TOPIC,
            Subject=f'[GuardDuty] {finding_type} - Instance {instance_id} Quarantined',
            Message=json.dumps({
                'action': 'instance_quarantined',
                'instance_id': instance_id,
                'finding_type': finding_type,
                'severity': severity,
                'account': account_id,
                'region': region,
                'original_security_groups': current_sgs,
                'description': finding.get('description', '')
            }, indent=2)
        )

        return {
            'statusCode': 200,
            'body': f'Instance {instance_id} quarantined and snapshots created'
        }

    return {'statusCode': 200, 'body': 'Non-EC2 finding processed'}

IAM Credential Compromise Response

import boto3
import json
import os

iam = boto3.client('iam')
sns = boto3.client('sns')

SNS_TOPIC = os.environ.get('SNS_TOPIC_ARN')

def lambda_handler(event, context):
    finding = event['detail']
    finding_type = finding['type']

    if 'IAMUser' not in finding_type and 'UnauthorizedAccess' not in finding_type:
        return {'statusCode': 200, 'body': 'Not an IAM finding'}

    resource = finding.get('resource', {})
    access_key_details = resource.get('accessKeyDetails', {})
    user_name = access_key_details.get('userName', '')
    access_key_id = access_key_details.get('accessKeyId', '')

    if not user_name:
        return {'statusCode': 200, 'body': 'No user identified'}

    actions_taken = []

    # Deactivate the compromised access key
    if access_key_id and access_key_id != 'GeneratedFindingAccessKeyId':
        try:
            iam.update_access_key(
                UserName=user_name,
                AccessKeyId=access_key_id,
                Status='Inactive'
            )
            actions_taken.append(f'Deactivated access key {access_key_id}')
        except Exception as e:
            actions_taken.append(f'Failed to deactivate key: {str(e)}')

    # Attach deny-all policy to user
    deny_policy = {
        "Version": "2012-10-17",
        "Statement": [{
            "Effect": "Deny",
            "Action": "*",
            "Resource": "*"
        }]
    }

    try:
        iam.put_user_policy(
            UserName=user_name,
            PolicyName='GuardDuty-DenyAll-Quarantine',
            PolicyDocument=json.dumps(deny_policy)
        )
        actions_taken.append(f'Applied deny-all policy to {user_name}')
    except Exception as e:
        actions_taken.append(f'Failed to apply deny policy: {str(e)}')

    # Notify
    sns.publish(
        TopicArn=SNS_TOPIC,
        Subject=f'[GuardDuty] IAM Compromise - {user_name}',
        Message=json.dumps({
            'finding_type': finding_type,
            'user': user_name,
            'access_key': access_key_id,
            'actions_taken': actions_taken,
            'severity': finding['severity']
        }, indent=2)
    )

    return {'statusCode': 200, 'body': json.dumps(actions_taken)}

Terraform Deployment

resource "aws_guardduty_detector" "main" {
  enable = true
  finding_publishing_frequency = "FIFTEEN_MINUTES"

  datasources {
    s3_logs { enable = true }
    kubernetes { audit_logs { enable = true } }
    malware_protection {
      scan_ec2_instance_with_findings {
        ebs_volumes { enable = true }
      }
    }
  }
}

resource "aws_cloudwatch_event_rule" "guardduty_high" {
  name        = "guardduty-high-severity"
  description = "GuardDuty high severity findings"

  event_pattern = jsonencode({
    source      = ["aws.guardduty"]
    detail-type = ["GuardDuty Finding"]
    detail = {
      severity = [{ numeric = [">=", 7.0] }]
    }
  })
}

resource "aws_cloudwatch_event_target" "lambda" {
  rule = aws_cloudwatch_event_rule.guardduty_high.name
  arn  = aws_lambda_function.guardduty_response.arn
}

Finding Categories

Multi-Account Setup

# Designate GuardDuty administrator
aws guardduty enable-organization-admin-account \
  --admin-account-id 111111111111

# Auto-enable for new accounts
aws guardduty update-organization-configuration \
  --detector-id DETECTOR_ID \
  --auto-enable

When NOT to Use

• You need to perform the attack to test detection (use performing-* skills)
• Task is about analyzing past incidents (use analyzing-* skills)
• You need to implement detection rules (use implementing-* skills)
• Task is about threat hunting proactively (use hunting-* skills)
• You don't have access to logs or monitoring data
• Task requires incident response (use IR skills)

Red Flags

• Performing actions without explicit written authorization from the asset owner
• Testing against production systems without a defined scope and rules of engagement
• Modifying cloud IAM policies or security groups without approval
• Exposing cloud credentials or secrets in logs or reports
• Running scans that generate excessive API calls and trigger billing alerts

Verification

• All steps executed successfully against a test environment before production use
• Output documented with screenshots or logs demonstrating expected behavior
• Cloud resource changes reverted or documented as intentional
• IAM policies reviewed for least-privilege compliance after testing
• No residual test resources left running (cost and security check)

References

• AWS GuardDuty Best Practices: https://aws.github.io/aws-security-services-best-practices/guides/guardduty/
• EventBridge Integration: https://docs.aws.amazon.com/guardduty/latest/ug/guardduty_findings_eventbridge.html
• GuardDuty Finding Types Reference

Process

1. Analyze the task requirements
2. Apply domain expertise
3. Verify output quality

Anti-Rationalization Table