/detecting-cloud-threats-with-guardduty

name: detecting-cloud-threats-with-guardduty
description: 'This skill teaches security teams how to deploy and operationalize Amazon GuardDuty for continuous threat detection
  across AWS accounts and workloads. It covers enabling protection plans for S3, EKS, EC2 runtime monitoring, and Lambda,
  interpreting finding severity levels, and building automated response workflows using EventBridge and Lambda.

  '
domain: cybersecurity
subdomain: cloud-security
tags:
- amazon-guardduty
- threat-detection
- aws-security
- runtime-monitoring
- cloud-soc
version: 1.0.0
author: mahipal
license: Apache-2.0
nist_csf:
- PR.IR-01
- ID.AM-08
- GV.SC-06
- DE.CM-01

Detecting Cloud Threats with GuardDuty

When to Use

• When establishing continuous threat detection for new or existing AWS accounts
• When investigating GuardDuty findings related to compromised instances, credential abuse, or data exfiltration
• When building automated incident response playbooks triggered by GuardDuty findings
• When extending threat coverage to container workloads running on EKS, ECS, or Fargate
• When enabling malware scanning for EBS volumes attached to suspicious EC2 instances

**Do not use** for Azure or GCP threat detection (see securing-azure-with-microsoft-defender or auditing-gcp-security-posture), for static code analysis, or for compliance posture monitoring (see implementing-aws-security-hub).

Prerequisites

• AWS account with GuardDuty administrative permissions (guardduty:*)
• AWS CloudTrail, VPC Flow Logs, and DNS query logs enabled (GuardDuty consumes these automatically)
• AWS Organizations configured if deploying GuardDuty across a multi-account estate
• EventBridge and Lambda configured for automated response workflows

Workflow

Step 1: Enable GuardDuty and Protection Plans

Activate GuardDuty at the organization level using a delegated administrator account. Enable all protection plans including S3 Protection, EKS Audit Log Monitoring, Runtime Monitoring, Malware Protection, RDS Login Activity, and Lambda Network Activity Monitoring.

# Enable GuardDuty as organization delegated administrator
aws guardduty create-detector \
  --enable \
  --finding-publishing-frequency FIFTEEN_MINUTES \
  --data-sources '{
    "S3Logs": {"Enable": true},
    "Kubernetes": {"AuditLogs": {"Enable": true}},
    "MalwareProtection": {"ScanEc2InstanceWithFindings": {"EbsVolumes": true}}
  }'

# Enable Runtime Monitoring for EC2 and ECS
aws guardduty update-detector \
  --detector-id <detector-id> \
  --features '[
    {"Name": "RUNTIME_MONITORING", "Status": "ENABLED",
     "AdditionalConfiguration": [
       {"Name": "ECS_FARGATE_AGENT_MANAGEMENT", "Status": "ENABLED"},
       {"Name": "EC2_AGENT_MANAGEMENT", "Status": "ENABLED"}
     ]}
  ]'

# Designate delegated admin for multi-account
aws guardduty enable-organization-admin-account \
  --admin-account-id 111122223333

Step 2: Configure Multi-Account Aggregation

Automatically enroll all organization member accounts and configure finding export to a centralized S3 bucket for retention and SIEM ingestion.

# Auto-enable GuardDuty for all org members
aws guardduty update-organization-configuration \
  --detector-id <detector-id> \
  --auto-enable-organization-members ALL \
  --features '[
    {"Name": "S3_DATA_EVENTS", "AutoEnable": "ALL"},
    {"Name": "EKS_AUDIT_LOGS", "AutoEnable": "ALL"},
    {"Name": "RUNTIME_MONITORING", "AutoEnable": "ALL"}
  ]'

# Configure finding export to S3
aws guardduty create-publishing-destination \
  --detector-id <detector-id> \
  --destination-type S3 \
  --destination-properties '{
    "DestinationArn": "arn:aws:s3:::guardduty-findings-centralized",
    "KmsKeyArn": "arn:aws:kms:us-east-1:123456789012:key/key-id"
  }'

Step 3: Interpret Finding Types and Severity Levels

GuardDuty classifies findings into four severity levels: Critical, High, Medium, and Low. Each finding type follows the format ThreatPurpose:ResourceType/ThreatName. Extended Threat Detection generates attack sequence findings that correlate multiple events across time.

Key finding categories:

• **Recon**: Port scanning, API enumeration (e.g., Recon:EC2/PortProbeUnprotectedPort)
• **UnauthorizedAccess**: Credential abuse, console logins from unusual locations
• **CryptoCurrency**: Mining activity detected on instances (e.g., CryptoCurrency:EC2/BitcoinTool.B)
• **Impact**: Resource hijacking, data destruction attempts
• **AttackSequence**: Multi-stage attacks correlating initial access through lateral movement to impact (Critical severity)

Step 4: Build Automated Response with EventBridge

Create EventBridge rules that route GuardDuty findings to Lambda functions for automated containment actions such as isolating compromised EC2 instances, revoking IAM credentials, or blocking malicious IP addresses.

# EventBridge rule for high/critical GuardDuty findings
aws events put-rule \
  --name GuardDutyHighSeverity \
  --event-pattern '{
    "source": ["aws.guardduty"],
    "detail-type": ["GuardDuty Finding"],
    "detail": {
      "severity": [{"numeric": [">=", 7]}]
    }
  }'

# Target Lambda function for auto-remediation
aws events put-targets \
  --rule GuardDutyHighSeverity \
  --targets '[{
    "Id": "AutoRemediateTarget",
    "Arn": "arn:aws:lambda:us-east-1:123456789012:function/guardduty-auto-remediate"
  }]'

Auto-remediation Lambda example for isolating a compromised EC2 instance:

import boto3

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

    if finding_type.startswith('UnauthorizedAccess:EC2') and severity >= 7:
        instance_id = finding['resource']['instanceDetails']['instanceId']
        ec2 = boto3.client('ec2')

        # Create isolation security group (no inbound/outbound rules)
        vpc_id = finding['resource']['instanceDetails']['networkInterfaces'][0]['vpcId']
        is