detecting-aws-guardduty-findings-automation

name	detecting-aws-guardduty-findings-automation
description	Automate AWS GuardDuty threat detection findings processing using EventBridge and Lambda to enable real-time incident response, automatic quarantine of compromised resources, and security notification workflows.
domain	cybersecurity
subdomain	cloud-security
tags	["aws","guardduty","eventbridge","lambda","threat-detection","automation","incident-response","siem"]
version	1.0
author	mahipal
license	Apache-2.0

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.

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

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

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'][][][][]]

        
        ec2.create_tags(
            Resources=[instance_id],
            Tags=[
                {: , : },
                {: , : finding_type},
                {: , : .join(current_sgs)},
                {: , : finding[]}
            ]
        )

        
         QUARANTINE_SG:
            ec2.modify_instance_attribute(
                InstanceId=instance_id,
                Groups=[QUARANTINE_SG]
            )

        
        volumes = ec2.describe_volumes(
            Filters=[{: , : [instance_id]}]
        )
         vol  volumes[]:
            ec2.create_snapshot(
                VolumeId=vol[],
                Description=,
                TagSpecifications=[{
                    : ,
                    : [
                        {: , : },
                        {: , : instance_id},
                        {: , : finding_type}
                    ]
                }]
            )

        
        sns.publish(
            TopicArn=SNS_TOPIC,
            Subject=,
            Message=json.dumps({
                : ,
                : instance_id,
                : finding_type,
                : severity,
                : account_id,
                : region,
                : current_sgs,
                : finding.get(, )
            }, indent=)
        )

         {
            : ,
            : 
        }

     {: , : }

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 ')
         Exception  e:
            actions_taken.append()

    
    deny_policy = {
        : ,
        : [{
            : ,
            : ,
            : 
        }]
    }

    :
        iam.put_user_policy(
            UserName=user_name,
            PolicyName=,
            PolicyDocument=json.dumps(deny_policy)
        )
        actions_taken.append()
     Exception  e:
        actions_taken.append()

    
    sns.publish(
        TopicArn=SNS_TOPIC,
        Subject=,
        Message=json.dumps({
            : finding_type,
            : user_name,
            : access_key_id,
            : actions_taken,
            : finding[]
        }, indent=)
    )

     {: , : 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

Category	Severity Range	Examples
Backdoor	5.0 - 8.0	Backdoor:EC2/C&CActivity
CryptoCurrency	5.0 - 8.0	CryptoCurrency:EC2/BitcoinTool
Trojan	5.0 - 8.0	Trojan:EC2/BlackholeTraffic
UnauthorizedAccess	5.0 - 8.0	UnauthorizedAccess:IAMUser/ConsoleLogin
Recon	2.0 - 5.0	Recon:EC2/PortProbeUnprotected
Persistence	5.0 - 8.0	Persistence:IAMUser/AnomalousBehavior

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

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