THIS IS A EXPERIMENTAL DETECTION
This detection has been marked experimental by the Splunk Threat Research team. This means we have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.
The following analytic detects potential instances that are created in a cloud computing environment using new or unknown image IDs that have not been seen before. This detection is important because it helps to investigate and take appropriate action to prevent further damage or unauthorized access to the Cloud environment, which can include data breaches, unauthorized access to sensitive information, or the deployment of malicious payloads within the cloud environment. False positives might occur since legitimate instances can also have previously unseen image IDs. Next steps include conducting an extensive triage and investigation to determine the nature of the activity. During triage, review the details of the created instances, including the user responsible for the creation, the image ID used, and any associated metadata. Additionally, consider inspecting any relevant on-disk artifacts and analyzing concurrent processes to identify the source of the attack.
- Type: Anomaly
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Change
- Last Updated: 2018-10-12
- Author: David Dorsey, Splunk
- ID: bc24922d-987c-4645-b288-f8c73ec194c4
Kill Chain Phase
- CIS 10
1 2 3 4 5 6 7 8 9 10 11 12 13 | 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`
The SPL above uses the following Macros:
cloud_compute_instance_created_with_previously_unseen_image_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
The SPL above uses the following Lookups:
List of fields required to use this analytic.
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
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.
Associated Analytic Story
|36.0||60||60||User $user$ is creating an instance $dest$ with an image that has not been previously seen.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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