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.

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

 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