Detection: EC2 Instance Started In Previously Unseen Region

DEPRECATED DETECTION

This detection has been marked as deprecated by the Splunk Threat Research team. This means that it will no longer be maintained or supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2024-10-17 ID: ada0f478-84a8-4641-a3f3-d82362d6fd75 Author: Bhavin Patel, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

This search looks for AWS CloudTrail events where an instance is started in a particular region in the last one hour and then compares it to a lookup file of previously seen regions where an instance was started

Search

 1`cloudtrail` earliest=-1h StartInstances 
 2| stats earliest(_time) as earliest latest(_time) as latest by awsRegion 
 3| inputlookup append=t previously_seen_aws_regions.csv 
 4| stats min(earliest) as earliest max(latest) as latest by awsRegion 
 5| outputlookup previously_seen_aws_regions.csv 
 6| eval regionStatus=if(earliest >= relative_time(now(),"-1d@d"), "Instance Started in a New Region","Previously Seen Region") 
 7| `security_content_ctime(earliest)` 
 8| `security_content_ctime(latest)` 
 9| where regionStatus="Instance Started in a New Region" 
10| `ec2_instance_started_in_previously_unseen_region_filter`

Data Source

No data sources specified for this detection.

Macros Used

Name	Value
cloudtrail	`sourcetype=aws:cloudtrail`
ec2_instance_started_in_previously_unseen_region_filter	`search *`

ec2_instance_started_in_previously_unseen_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_13

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 install the AWS App for Splunk (version 5.1.0 or later) and Splunk Add-on for AWS (version 4.4.0 or later), then configure your AWS CloudTrail inputs. Run the "Previously seen AWS Regions" support search only once to create of baseline of previously seen regions. This search is deprecated and have been translated to use the latest Change Datamodel.

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
tbd	25	50	50

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	❌ Failing	N/A	`N/A`	`N/A`
Integration	❌ Failing	N/A	`N/A`	`N/A`

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