Cloud Instance Modified By Previously Unseen User

name: Cloud Instance Modified By Previously Unseen User
id: 7fb15084-b14e-405a-bd61-a6de15a40722
version: 12
creation_date: '2020-11-16'
modification_date: '2026-05-13'
author: Rico Valdez, Splunk
status: production
type: Anomaly
description: The following analytic identifies cloud instances being modified by users who have not previously modified them. It leverages data from the Change data model, focusing on successful modifications of EC2 instances. This activity is significant because it can indicate unauthorized or suspicious changes by potentially compromised or malicious users. If confirmed malicious, this could lead to unauthorized access, configuration changes, or potential disruption of cloud services, posing a significant risk to the organization's cloud infrastructure.
data_source:
    - AWS CloudTrail
search: |-
    | tstats `security_content_summariesonly` count earliest(_time) as firstTime, latest(_time) as lastTime values(All_Changes.object_id) as object_id values(All_Changes.command) as command FROM datamodel=Change
      WHERE All_Changes.action=modified All_Changes.change_type=EC2 All_Changes.status=success
      BY All_Changes.user
    | `drop_dm_object_name("All_Changes")`
    | lookup previously_seen_cloud_instance_modifications_by_user user as user OUTPUTNEW firstTimeSeen, enough_data
    | eventstats max(enough_data) as enough_data
    | where enough_data=1
    | eval firstTimeSeenUser=min(firstTimeSeen)
    | where isnull(firstTimeSeenUser) OR firstTimeSeenUser > relative_time(now(), "-24h@h")
    | table firstTime user command object_id count
    | `security_content_ctime(firstTime)`
    | `cloud_instance_modified_by_previously_unseen_user_filter`
how_to_implement: This search has a dependency on other searches to create and update a baseline of users observed to be associated with this activity. The search "Previously Seen Cloud Instance Modifications By User - Update" should be enabled for this detection to properly work.
known_false_positives: It's possible that a new user will start to modify EC2 instances when they haven't before for any number of reasons. Verify with the user that is modifying instances that this is the intended behavior.
references: []
intermediate_findings:
    entities:
        - field: user
          type: user
          score: 20
          message: User $user$ is modifying an instance $object_id$ for the first time.
analytic_story:
    - Suspicious Cloud Instance Activities
asset_type: AWS Instance
mitre_attack_id:
    - T1078.004
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: threat
baselines:
    - Previously Seen Cloud Instance Modifications By User - Update
    - Previously Seen Cloud Instance Modifications By User - Initial