Detection: Cloud Compute Instance Created In Previously Unused Region

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: 2024-10-17 ID: fa4089e2-50e3-40f7-8469-d2cc1564ca59 Author: David Dorsey, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects the creation of a cloud compute instance in a region that has not been previously used within the last hour. It leverages cloud infrastructure logs and compares the regions of newly created instances against a lookup file of historically used regions. This activity is significant because the creation of instances in new regions can indicate unauthorized or suspicious activity, such as an attacker attempting to evade detection or establish a foothold in a less monitored area. If confirmed malicious, this could lead to unauthorized resource usage, data exfiltration, or further compromise of the cloud environment.

 1
 2| tstats earliest(_time) as firstTime latest(_time) as lastTime values(All_Changes.object_id) as dest, count from datamodel=Change where All_Changes.action=created by All_Changes.vendor_region, All_Changes.user 
 3| `drop_dm_object_name("All_Changes")` 
 4| lookup previously_seen_cloud_regions vendor_region as vendor_region OUTPUTNEW firstTimeSeen, enough_data 
 5| eventstats max(enough_data) as enough_data 
 6| where enough_data=1 
 7| eval firstTimeSeenRegion=min(firstTimeSeen) 
 8| where isnull(firstTimeSeenRegion) OR firstTimeSeenRegion > relative_time(now(), "-24h@h") 
 9| table firstTime, user, dest, count , vendor_region 
10| `security_content_ctime(firstTime)` 
11| `cloud_compute_instance_created_in_previously_unused_region_filter`

Data Source

Name Platform Sourcetype Source
AWS CloudTrail AWS icon AWS 'aws:cloudtrail' 'aws_cloudtrail'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
cloud_compute_instance_created_in_previously_unused_region_filter search *
cloud_compute_instance_created_in_previously_unused_region_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
T1535 Unused/Unsupported Cloud Regions Defense Evasion
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10

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

You must be ingesting your cloud infrastructure logs from your cloud provider. You should run the baseline search Previously Seen Cloud Regions - Initial to build the initial table of images observed and times. You must also enable the second baseline search Previously Seen Cloud Regions - Update to keep this table up to date and to age out old data. You can also provide additional filtering for this search by customizing the cloud_compute_instance_created_in_previously_unused_region_filter macro.

Known False Positives

It's possible that a user has unknowingly started an instance in a new region. Please verify that this activity is legitimate.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
User $user$ is creating an instance $dest$ in a new region 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