splunk-security_content/docs/_posts/2020-11-09-common_ransomware_notes.md

title, excerpt, categories, last_modified_at, toc, toc_label, tags

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Common Ransomware Notes	Data Destruction	Endpoint	2020-11-09	true		Data Destruction Impact Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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Description

The search looks for files created with names matching those typically used in ransomware notes that tell the victim how to get their data back.

• Type: Hunting
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2020-11-09
• Author: David Dorsey, Splunk
• ID: ada0f478-84a8-4641-a3f1-d82362d6bd71

Annotations

ATT&CK

ID	Technique	Tactic
T1485	Data Destruction	Impact

Kill Chain Phase

• Actions on Objectives

NIST

• PR.PT
• DE.CM

CIS20

• CIS 8

CVE

Search

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime values(Filesystem.user) as user values(Filesystem.dest) as dest values(Filesystem.file_path) as file_path from datamodel=Endpoint.Filesystem by Filesystem.file_name 
| `drop_dm_object_name(Filesystem)` 
| `security_content_ctime(lastTime)` 
| `security_content_ctime(firstTime)` 
| `ransomware_notes` 
| `common_ransomware_notes_filter`

Macros

The SPL above uses the following Macros:

• ransomware_notes
• security_content_ctime
• security_content_summariesonly

ℹ️ common_ransomware_notes_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

• _time
• Filesystem.user
• Filesystem.dest
• Filesystem.file_path
• Filesystem.file_name

How To Implement

You must be ingesting data that records file-system activity from your hosts to populate the Endpoint Filesystem data-model node. This is typically populated via endpoint detection-and-response product, such as Carbon Black, or via other endpoint data sources, such as Sysmon. The data used for this search is typically generated via logs that report file-system reads and writes.

Known False Positives

It's possible that a legitimate file could be created with the same name used by ransomware note files.

Associated Analytic story

• SamSam Ransomware
• Ransomware
• Ryuk Ransomware
• Clop Ransomware

RBA

Risk Score	Impact	Confidence	Message
90.0	90	100	A file - file_name was written to disk on endpoint dest by user user, this is indicative of a known ransomware note file and should be reviewed immediately.

ℹ️ The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1485/ransomware_notes/windows-sysmon.log

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