AWS SetDefaultPolicyVersion

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

The following analytic detects when a user sets a default policy version in AWS. It leverages AWS CloudTrail logs to identify the `SetDefaultPolicyVersion` event from the IAM service. This activity is significant because attackers may exploit this technique for privilege escalation, especially if previous policy versions grant more extensive permissions than the current one. If confirmed malicious, this could allow an attacker to gain elevated access to AWS resources, potentially leading to unauthorized actions and data breaches.

name: AWS SetDefaultPolicyVersion
id: 2a9b80d3-6340-4345-11ad-212bf3d0dac4
version: 11
creation_date: '2021-03-02'
modification_date: '2026-05-13'
author: Bhavin Patel, Splunk
status: production
type: TTP
description: The following analytic detects when a user sets a default policy version in AWS. It leverages AWS CloudTrail logs to identify the `SetDefaultPolicyVersion` event from the IAM service. This activity is significant because attackers may exploit this technique for privilege escalation, especially if previous policy versions grant more extensive permissions than the current one. If confirmed malicious, this could allow an attacker to gain elevated access to AWS resources, potentially leading to unauthorized actions and data breaches.
data_source:
    - AWS CloudTrail SetDefaultPolicyVersion
search: |-
    `cloudtrail` eventName=SetDefaultPolicyVersion eventSource = iam.amazonaws.com
      | rename user_name as user
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY signature dest user
           user_agent src vendor_account
           vendor_region vendor_product
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `aws_setdefaultpolicyversion_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: While this search has no known false positives, it is possible that an AWS admin has legitimately set a default policy to allow a user to access all resources. That said, AWS strongly advises against granting full control to all AWS resources
references:
    - https://bishopfox.com/blog/privilege-escalation-in-aws
    - https://rhinosecuritylabs.com/aws/aws-privilege-escalation-methods-mitigation-part-2/
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: From IP address $src$, user $user$ has trigged an action $signature$ for updating the the default policy version
    entity:
        field: user
        type: user
        score: 50
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - AWS IAM Privilege Escalation
asset_type: AWS Account
mitre_attack_id:
    - T1078.004
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/T1078/aws_setdefaultpolicyversion/aws_cloudtrail_events.json
          sourcetype: aws:cloudtrail
          source: aws_cloudtrail
      test_type: unit

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