What it does. Build automated AWS GuardDuty finding response pipelines using EventBridge Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).

Install

• npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill detecting-aws-guardduty-findings-automation, or copy the skill folder into ~/.claude/skills/detecting-aws-guardduty-findings-automation/.
• Raw file: curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/detecting-aws-guardduty-findings-automation/SKILL.md

SKILL.md (verbatim)

name: detecting-aws-guardduty-findings-automation
description: Build automated AWS GuardDuty finding response pipelines using EventBridge
  and Lambda to trigger real-time incident response, automatically quarantine compromised
  resources, and route security notifications. Use when designing automated remediation
  playbooks for GuardDuty findings across VPC Flow Logs, CloudTrail, DNS, EKS, or S3
  data events, or when reducing mean time to respond to cloud threats.
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
nist_csf:
- PR.IR-01
- ID.AM-08
- GV.SC-06
- DE.CM-01
mitre_attack:
- T1078.004
- T1496
- T1580
- T1530
- T1110

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

• 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

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'][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

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

Other files in this skill

• LICENSE
• assets/template.md
• references/api-reference.md
• references/standards.md
• references/workflows.md
• scripts/agent.py
• scripts/process.py

assets/template.md (verbatim)

GuardDuty Findings Automation Template

Configuration

EventBridge Rules

Auto-Response Actions

references/api-reference.md (verbatim)

AWS GuardDuty Findings Automation — API Reference

Libraries

Key boto3 GuardDuty Methods

Finding Severity Levels

GuardDuty Finding Types

GuardDuty Protection Features

FindingCriteria Filter

criteria = {
    "Criterion": {
        "severity": {"Gte": 7.0},
        "service.archived": {"Eq": ["false"]},
        "type": {"Eq": ["UnauthorizedAccess:EC2/SSHBruteForce"]},
    }
}

External References

• GuardDuty API Reference
• GuardDuty Finding Types
• GuardDuty Multi-Account

references/standards.md (verbatim)

Standards - AWS GuardDuty Findings Automation

MITRE ATT&CK Mapping

• TA0001 Initial Access: UnauthorizedAccess findings
• TA0003 Persistence: Persistence:IAMUser findings
• TA0005 Defense Evasion: Stealth findings
• TA0006 Credential Access: CredentialAccess findings
• TA0010 Exfiltration: Exfiltration findings
• TA0040 Impact: CryptoCurrency/Trojan findings

NIST 800-53

• IR-4: Incident Handling
• IR-5: Incident Monitoring
• SI-4: System Monitoring
• AU-6: Audit Record Review

AWS Security Best Practices

• Enable GuardDuty in all regions
• Configure multi-account with Organizations
• Publish findings every 15 minutes
• Integrate with Security Hub

references/workflows.md (verbatim)

Workflows - AWS GuardDuty Findings Automation

Automated Response Workflow

1. GuardDuty detects threat → Generates finding
2. EventBridge receives finding event
3. EventBridge routes to Lambda based on severity/type
4. Lambda executes automated response:
   - EC2: Quarantine instance, snapshot volumes
   - IAM: Deactivate keys, apply deny policy
   - S3: Block public access, enable versioning
5. SNS notifies security team
6. Finding synced to Security Hub
7. Analyst reviews and confirms actions

Triage Workflow

1. HIGH (7-8.9): Immediate auto-response + page on-call
2. MEDIUM (4-6.9): Auto-notify + queue for review
3. LOW (1-3.9): Log and batch review weekly

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