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Description

This search looks for cloud compute instances being created with previously unseen image IDs.

  • Type: Anomaly
  • Product: Splunk Security Analytics for AWS, Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Change
  • Last Updated: 2018-10-12
  • Author: David Dorsey, Splunk
  • ID: bc24922d-987c-4645-b288-f8c73ec194c4

| tstats count earliest(_time) as firstTime, latest(_time) as lastTime values(All_Changes.object_id) as dest from datamodel=Change where All_Changes.action=created by All_Changes.Instance_Changes.image_id, All_Changes.user 
| `drop_dm_object_name("All_Changes")` 
| `drop_dm_object_name("Instance_Changes")` 
| where image_id != "unknown" 
| lookup previously_seen_cloud_compute_images image_id as image_id OUTPUT firstTimeSeen, enough_data 
| eventstats max(enough_data) as enough_data 
| where enough_data=1 
| eval firstTimeSeenImage=min(firstTimeSeen) 
| where isnull(firstTimeSeenImage) OR firstTimeSeenImage > relative_time(now(), "-24h@h") 
| table firstTime, user, image_id, count, dest 
| `security_content_ctime(firstTime)` 
| `cloud_compute_instance_created_with_previously_unseen_image_filter`

Associated Analytic Story

How To Implement

You must be ingesting your cloud infrastructure logs from your cloud provider. You should run the baseline search Previously Seen Cloud Compute Images - Initial to build the initial table of images observed and times. You must also enable the second baseline search Previously Seen Cloud Compute Images - 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_with_previously_unseen_image_filter macro.

Required field

  • _time
  • All_Changes.object_id
  • All_Changes.action
  • All_Changes.Instance_Changes.image_id
  • All_Changes.user

Kill Chain Phase

Known False Positives

After a new image is created, the first systems created with that image will cause this alert to fire. Verify that the image being used was created by a legitimate user.

RBA

Risk Score Impact Confidence Message
36.0 60 60 User $user$ is creating an instance $dest$ with an image that has not been previously seen.

Reference

Test Dataset

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

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