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AWS GuardDuty Security

THREAT DETECTION

GuardDuty is AWS's managed threat detection service. It analyzes CloudTrail, VPC Flow Logs, and DNS logs to detect malicious activity. Red teamers must understand what triggers alerts.

ML-Based

Detection

100+

Finding Types

Data Sources

~15 min

Detection Delay

📋Service Overview

CloudTrail Analysis

Analyzes management events for suspicious API activity: unusual regions, first-time API calls, known malicious IPs, credential abuse patterns.

VPC Flow Logs

Detects network anomalies: port scanning, unusual outbound traffic, communication with known C2 servers, cryptocurrency mining patterns.

DNS Logs

Monitors DNS queries for: C2 domain lookups, DNS exfiltration attempts, cryptomining pool connections, DGA domain patterns.

Security Risk Assessment

LowMediumHighCritical

7.0

Risk Score

GuardDuty can be disabled, findings can be archived/suppressed, and detection has blind spots. Understanding finding types helps red teamers operate below detection thresholds.

⚔️Attack Vectors

Disable Detection

•Disable GuardDuty detector entirely
•Suspend GuardDuty in specific regions
•Delete detector to stop all findings
•Remove member accounts from org detector
•Modify publishing destination

Suppress Findings

•Archive findings to hide them
•Create suppression rules for your IPs
•Add attacker IPs to trusted IP list
•Mark findings as "useful" to reduce noise
•Modify S3 publication frequency

👻Evasion Techniques

Behavioral Evasion

•Stay within normal API call patterns
•Use same regions as legitimate users
•Avoid known malicious IP addresses
•Throttle reconnaissance to avoid spikes
•Blend with existing traffic patterns

Technical Evasion

•Use residential proxies, not VPNs
•Avoid Tor exit nodes (flagged)
•DNS over HTTPS to bypass DNS analysis
•Encrypt C2 traffic to avoid pattern detection
•Use legitimate AWS services as proxies

🔍Enumeration

List Detectors

aws guardduty list-detectors

Get Detector Details

aws guardduty get-detector --detector-id abc123

List Findings

aws guardduty list-findings \
  --detector-id abc123 \
  --finding-criteria '{"Criterion":{"severity":{"Gte":7}}}'

List IP Sets (Trusted/Threat)

aws guardduty list-ip-sets --detector-id abc123

List Suppression Rules

aws guardduty list-filters --detector-id abc123

🚨Key Finding Types

IAM Findings

•UnauthorizedAccess:IAMUser/InstanceCredentialExfiltration
•Recon:IAMUser/MaliciousIPCaller
•PenTest:IAMUser/KaliLinux
•Persistence:IAMUser/AnomalousBehavior
•PrivilegeEscalation:IAMUser/AnomalousBehavior

EC2/Network Findings

•CryptoCurrency:EC2/BitcoinTool.B!DNS
•Backdoor:EC2/C&CActivity.B!DNS
•Trojan:EC2/DNSDataExfiltration
•UnauthorizedAccess:EC2/SSHBruteForce
•Impact:EC2/PortSweep

⚡Common Triggers

Will Trigger GuardDuty

•API calls from Tor exit nodes
•Calls from known malicious IPs
•First-time API in unusual region
•EC2 credential use outside AWS
•DNS queries to known C2 domains
•Port scanning from EC2 instances

May NOT Trigger

•API calls from residential IPs
•Slow, low-volume reconnaissance
•Traffic to non-blacklisted domains
•Actions matching normal patterns
•Encrypted exfiltration channels

🛡️Detection

CloudTrail Events to Monitor

•DeleteDetector - detector deleted
•UpdateDetector - settings changed
•ArchiveFindings - findings hidden
•CreateFilter - suppression rule added
•CreateIPSet - trusted IP list modified

Indicators of Tampering

•GuardDuty disabled unexpectedly
•New suppression filters created
•Findings archived in bulk
•Trusted IP list expanded
•Threat IP list deleted

📊GuardDuty Finding Severity Levels

High (7.0 - 8.9)

• Active credential compromise
• EC2 instance communicating with C2
• Cryptocurrency mining detected
• Data exfiltration in progress
• Backdoor activity detected

Response: Immediate investigation required

Medium (4.0 - 6.9)

• Unusual API activity patterns
• Suspicious network behavior
• Reconnaissance activity
• Potential policy violations
• Anomalous user behavior

Response: Investigate within 24 hours

Low (1.0 - 3.9)

• Informational findings
• Minor policy deviations
• Low-confidence detections
• Potential false positives
• Background noise

Response: Review during normal operations

💻Tampering Commands

Disable GuardDuty Detector

aws guardduty update-detector \
  --detector-id abc123 \
  --no-enable

Delete GuardDuty Detector

aws guardduty delete-detector --detector-id abc123

Archive All Findings

aws guardduty archive-findings \
  --detector-id abc123 \
  --finding-ids $(aws guardduty list-findings --detector-id abc123 --query 'FindingIds' --output text)

Create Suppression Rule

aws guardduty create-filter \
  --detector-id abc123 \
  --name "SuppressMyIP" \
  --action ARCHIVE \
  --finding-criteria '{"Criterion":{"service.action.networkConnectionAction.remoteIpDetails.ipAddressV4":{"Eq":["1.2.3.4"]}}}'

Add Trusted IP

aws guardduty create-ip-set \
  --detector-id abc123 \
  --name "TrustedIPs" \
  --format TXT \
  --location s3://bucket/trusted-ips.txt \
  --activate

Delete Threat IP List

aws guardduty delete-threat-intel-set \
  --detector-id abc123 \
  --threat-intel-set-id threat123

📜GuardDuty Policy Examples

✗Dangerous - Can Disable GuardDuty

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": "guardduty:*",
    "Resource": "*"
  }]
}

Full GuardDuty access allows disabling detection and suppressing findings

✓Read-Only - Security Monitoring

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": [
      "guardduty:Get*",
      "guardduty:List*",
      "guardduty:Describe*"
    ],
    "Resource": "*"
  }]
}

Read-only access for security analysts without modification rights

✓SCP - Prevent GuardDuty Disable

{
  "Version": "2012-10-17",
  "Statement": [{
    "Sid": "PreventGuardDutyDisable",
    "Effect": "Deny",
    "Action": [
      "guardduty:DeleteDetector",
      "guardduty:UpdateDetector",
      "guardduty:DeleteMembers",
      "guardduty:DisassociateFromMasterAccount"
    ],
    "Resource": "*"
  }]
}

Organization SCP to prevent disabling GuardDuty in member accounts

✗Dangerous - Can Suppress Findings

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": [
      "guardduty:ArchiveFindings",
      "guardduty:CreateFilter",
      "guardduty:UpdateFilter"
    ],
    "Resource": "*"
  }]
}

Ability to archive findings and create suppression rules hides attacks

🛡️Defense Recommendations

🏢

Use Organization Delegated Admin

Centralize GuardDuty management so member accounts can't disable it.

aws guardduty enable-organization-admin-account \
  --admin-account-id 123456789012

🔒

SCP to Prevent Tampering

Use Service Control Policies to deny GuardDuty modifications.

📊

Export Findings to S3/SIEM

Publish findings to S3 or EventBridge for independent monitoring.

aws guardduty create-publishing-destination \
  --detector-id abc123 \
  --destination-type S3 \
  --destination-properties DestinationArn=arn:aws:s3:::findings-bucket

🔔

Alert on GuardDuty Changes

Create CloudWatch alarms for DeleteDetector, UpdateDetector, ArchiveFindings.

🌍

Enable in All Regions

GuardDuty must be enabled per-region - ensure coverage everywhere.

for region in $(aws ec2 describe-regions --query 'Regions[].RegionName' --output text); do
  aws guardduty create-detector --enable --region $region
done

🎯

Configure Threat Intel Feeds

Add custom threat IP lists for your industry or known adversaries.

AWS GuardDuty Security Card • Toc Consulting

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