| ID | Technique | Tactic |
|---|---|---|
| T1078.004 | Cloud Accounts | Defense Evasion |
Detection: EC2 Instance Started With Previously Unseen User
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 EC2 instances being created by users who have not created them before. This search is deprecated and have been translated to use the latest Change Datamodel.
Search
1`cloudtrail` eventName=RunInstances [search `cloudtrail` eventName=RunInstances errorCode=success
2| stats earliest(_time) as firstTime latest(_time) as lastTime by userIdentity.arn
3| rename userIdentity.arn as arn
4| inputlookup append=t previously_seen_ec2_launches_by_user.csv
5| stats min(firstTime) as firstTime, max(lastTime) as lastTime by arn
6| outputlookup previously_seen_ec2_launches_by_user.csv
7| eval newUser=if(firstTime >= relative_time(now(), "-70m@m"), 1, 0)
8| where newUser=1
9| `security_content_ctime(firstTime)`
10| `security_content_ctime(lastTime)`
11| rename arn as userIdentity.arn
12| table userIdentity.arn]
13| rename requestParameters.instanceType as instanceType, responseElements.instancesSet.items{}.instanceId as dest, userIdentity.arn as user
14| table _time, user, dest, instanceType
15| `ec2_instance_started_with_previously_unseen_user_filter`
Data Source
No data sources specified for this detection.
Macros Used
| Name | Value |
|---|---|
| cloudtrail | sourcetype=aws:cloudtrail |
| ec2_instance_started_with_previously_unseen_user_filter | search * |
ec2_instance_started_with_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
KillChainPhase.DELIVERY
KillChainPhase.EXPLOITAITON
KillChainPhase.INSTALLATION
NistCategory.DE_AE
Cis18Value.CIS_10
APT28
APT29
APT33
APT5
Ke3chang
LAPSUS$
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. This search works best when you run the "Previously Seen EC2 Launches By User" support search once to create a history of previously seen ARNs.
Known False Positives
It's possible that a user will start to create EC2 instances when they haven't before for any number of reasons. Verify with the user that is launching instances that this is the intended behavior.
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: 4