splunk-security_content/detections/endpoint/common_ransomware_notes.yml

name: Common Ransomware Notes
id: ada0f478-84a8-4641-a3f1-d82362d6bd71
version: 4
date: '2020-11-09'
author: David Dorsey, Splunk
type: Hunting
datamodel:
- Endpoint
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.
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`'
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.
references: []
tags:
  Consequence: Data Destruction
  analytic_story:
  - SamSam Ransomware
  - Ransomware
  - Ryuk Ransomware
  - Clop Ransomware
  asset_type: Endpoint
  cis20:
  - CIS 8
  confidence: 100
  context:
  - Source:Endpoint
  - Stage:Execution
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1485/ransomware_notes/windows-sysmon.log
  impact: 90
  kill_chain_phases:
  - Actions on Objectives
  message: 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.
  mitre_attack_id:
  - T1485
  nist:
  - PR.PT
  - DE.CM
  observable:
  - name: user
    type: User
    role:
    - Victim
  - name: dest
    type: Hostname
    role:
    - Victim
  - name: file_name
    type: File Name
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Filesystem.user
  - Filesystem.dest
  - Filesystem.file_path
  - Filesystem.file_name
  risk_score: 90
  security_domain: endpoint