AWS AMI Attribute Modification for Exfiltration

SPLUNK detection rule by Bhavin Patel, Splunk · Apache-2.0

The following analytic detects suspicious modifications to AWS AMI attributes, such as sharing an AMI with another AWS account or making it publicly accessible. It leverages AWS CloudTrail logs to identify these changes by monitoring specific API calls. This activity is significant because adversaries can exploit these modifications to exfiltrate sensitive data stored in AWS resources. If confirmed malicious, this could lead to unauthorized access and potential data breaches, compromising the confidentiality and integrity of organizational information.

name: AWS AMI Attribute Modification for Exfiltration
id: f2132d74-cf81-4c5e-8799-ab069e67dc9f
version: 11
creation_date: '2023-03-31'
modification_date: '2026-05-13'
author: Bhavin Patel, Splunk
status: production
type: TTP
description: The following analytic detects suspicious modifications to AWS AMI attributes, such as sharing an AMI with another AWS account or making it publicly accessible. It leverages AWS CloudTrail logs to identify these changes by monitoring specific API calls. This activity is significant because adversaries can exploit these modifications to exfiltrate sensitive data stored in AWS resources. If confirmed malicious, this could lead to unauthorized access and potential data breaches, compromising the confidentiality and integrity of organizational information.
data_source:
    - AWS CloudTrail ModifyImageAttribute
search: |-
    `cloudtrail` eventName=ModifyImageAttribute (requestParameters.launchPermission.add.items{}.userId = * OR requestParameters.launchPermission.add.items{}.group = all)
      | rename requestParameters.launchPermission.add.items{}.group as group_added
      | rename requestParameters.launchPermission.add.items{}.userId as accounts_added
      | eval ami_status=if(match(group_added,"all") ,"Public AMI", "Not Public")
      | rename user_name as user
      | stats count min(_time) as firstTime max(_time) as lastTime values(group_added) as group_added values(accounts_added) as accounts_added values(ami_status) as ami_status
        BY signature dest user
           user_agent src vendor_account
           vendor_region vendor_product
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `aws_ami_attribute_modification_for_exfiltration_filter`
how_to_implement: You must install splunk AWS add on and Splunk App for AWS. This search works with AWS CloudTrail logs.
known_false_positives: It is possible that an AWS admin has legitimately shared a snapshot with others for  a specific purpose.
references:
    - https://labs.nettitude.com/blog/how-to-exfiltrate-aws-ec2-data/
    - https://stratus-red-team.cloud/attack-techniques/AWS/aws.exfiltration.ec2-share-ami/
    - https://hackingthe.cloud/aws/enumeration/loot_public_ebs_snapshots/
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: AWS AMI from account $vendor_account$ is shared externally with $accounts_added$ from $src$ or AMI made is made Public.
    entity:
        field: user
        type: user
        score: 50
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - Suspicious Cloud Instance Activities
    - Data Exfiltration
asset_type: EC2 Snapshot
mitre_attack_id:
    - T1537
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1537/aws_ami_shared_public/aws_cloudtrail_events.json
          sourcetype: aws:cloudtrail
          source: aws_cloudtrail
      test_type: unit

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