Detection: Cloud Instance Modified By Previously Unseen User

EXPERIMENTAL DETECTION

This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2024-08-16 ID: 7fb15084-b14e-405a-bd61-a6de15a40722 Author: Rico Valdez, Splunk Type: Anomaly Product: Splunk Enterprise Security

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.

Search

 1
 2| 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 
 3| `drop_dm_object_name("All_Changes")` 
 4| lookup previously_seen_cloud_instance_modifications_by_user user as user OUTPUTNEW firstTimeSeen, enough_data 
 5| eventstats max(enough_data) as enough_data 
 6| where enough_data=1 
 7| eval firstTimeSeenUser=min(firstTimeSeen) 
 8| where isnull(firstTimeSeenUser) OR firstTimeSeenUser > relative_time(now(), "-24h@h") 
 9| table firstTime user command object_id count 
10| `security_content_ctime(firstTime)` 
11| `cloud_instance_modified_by_previously_unseen_user_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
AWS CloudTrail	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
cloud_instance_modified_by_previously_unseen_user_filter	`search *`

cloud_instance_modified_by_previously_unseen_user_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1078.004	Cloud Accounts	Defense Evasion
T1078	Valid Accounts	Initial Access

KillChainPhase.DELIVERY

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_AE

Cis18Value.CIS_10

APT28

APT29

APT33

APT5

Ke3chang

LAPSUS$

APT18

APT28

APT29

APT33

APT39

APT41

Akira

Axiom

Carbanak

Chimera

Cinnamon Tempest

Dragonfly

FIN10

FIN4

FIN5

FIN6

FIN7

FIN8

Fox Kitten

GALLIUM

Ke3chang

LAPSUS$

Lazarus Group

Leviathan

OilRig

POLONIUM

PittyTiger

Sandworm Team

Silence

Silent Librarian

Suckfly

Threat Group-3390

Wizard Spider

menuPass

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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.

Associated Analytic Story

Suspicious Cloud Instance Activities

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
User $user$ is modifying an instance $object_id$ for the first time.	42	70	60

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

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`aws_cloudtrail`	`aws:cloudtrail`
Integration	✅ Passing	Dataset	`aws_cloudtrail`	`aws:cloudtrail`

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: GitHub | Version: 3