ID | Technique | Tactic |
---|
Detection: EC2 Instance Started With Previously Unseen AMI
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 with previously unseen AMIs. 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 requestParameters.instancesSet.items{}.imageId
3| rename requestParameters.instancesSet.items{}.imageId as amiID
4| inputlookup append=t previously_seen_ec2_amis.csv
5| stats min(firstTime) as firstTime max(lastTime) as lastTime by amiID
6| outputlookup previously_seen_ec2_amis.csv
7| eval newAMI=if(firstTime >= relative_time(now(), "-70m@m"), 1, 0)
8| `security_content_ctime(firstTime)`
9|`security_content_ctime(lastTime)`
10| where newAMI=1
11| rename amiID as requestParameters.instancesSet.items{}.imageId
12| table requestParameters.instancesSet.items{}.imageId]
13| rename requestParameters.instanceType as instanceType, responseElements.instancesSet.items{}.instanceId as dest, userIdentity.arn as arn, requestParameters.instancesSet.items{}.imageId as amiID
14| table firstTime, lastTime, arn, amiID, dest, instanceType
15| `ec2_instance_started_with_previously_unseen_ami_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
N/A | N/A | N/A | N/A | N/A |
Macros Used
Name | Value |
---|---|
cloudtrail | sourcetype=aws:cloudtrail |
ec2_instance_started_with_previously_unseen_ami_filter | search * |
ec2_instance_started_with_previously_unseen_ami_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 |
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 AMIs" support search once to create a history of previously seen AMIs.
Known False Positives
After a new AMI is created, the first systems created with that AMI will cause this alert to fire. Verify that the AMI being used was created by a legitimate user.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
tbd | 25 | 50 | 50 |
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: 2