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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.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-09
  • Author: Bhavin Patel, Splunk
  • ID: f2132d74-cf81-4c5e-8799-ab069e67dc9f

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1537 Transfer Data to Cloud Account Exfiltration
Kill Chain Phase
  • Actions On Objectives
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`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")  
| stats count min(_time) as firstTime max(_time) as lastTime  values(group_added) values(accounts_added) as accounts_added values(ami_status) by  src_ip region eventName userAgent user_arn aws_account_id userIdentity.principalId 
|  `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)` 
| `aws_ami_attribute_modification_for_exfiltration_filter`

Macros

The SPL above uses the following Macros:

:information_source: aws_ami_attribute_modification_for_exfiltration_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • eventName
  • user_arn
  • src_ip
  • requestParameters.attributeType
  • aws_account_id
  • vendor_region
  • user_agent
  • userIdentity.principalId

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.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
80.0 100 80 AWS AMI from account $aws_account_id$ is shared externally with $accounts_added$ from $src_ip$ or AMI made is made Public.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 3