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windows_diskcryptor_usage.yml
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windows_diskcryptor_usage.yml
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name: Windows DiskCryptor Usage
id: d56fe0c8-4650-11ec-a8fa-acde48001122
version: 1
date: '2021-11-15'
author: Michael Haag, Splunk
status: production
type: Hunting
description: The following analytic identifies DiskCryptor process name of dcrypt.exe
or internal name dcinst.exe. This utility has been utilized by adversaries to encrypt
disks manually during an operation. In addition, during install, a dcrypt.sys driver
is installed and requires a reboot in order to take effect. There are no command-line
arguments used.
data_source:
- Sysmon EventID 1
search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
as lastTime from datamodel=Endpoint.Processes where (Processes.process_name="dcrypt.exe"
OR Processes.original_file_name=dcinst.exe) by Processes.dest Processes.user Processes.parent_process_name
Processes.process_name Processes.original_file_name Processes.process Processes.process_id
Processes.parent_process_id | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)` | `windows_diskcryptor_usage_filter`'
how_to_implement: The detection is based on data that originates from Endpoint Detection
and Response (EDR) agents. These agents are designed to provide security-related
telemetry from the endpoints where the agent is installed. To implement this search,
you must ingest logs that contain the process GUID, process name, and parent process.
Additionally, you must ingest complete command-line executions. These logs must
be processed using the appropriate Splunk Technology Add-ons that are specific to
the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint`
data model. Use the Splunk Common Information Model (CIM) to normalize the field
names and speed up the data modeling process.
known_false_positives: It is possible false positives may be present based on the
internal name dcinst.exe, filter as needed. It may be worthy to alert on the service
name.
references:
- https://thedfirreport.com/2021/11/15/exchange-exploit-leads-to-domain-wide-ransomware/
- https://github.com/DavidXanatos/DiskCryptor
tags:
analytic_story:
- Ransomware
asset_type: Endpoint
confidence: 50
impact: 70
message: An instance of $parent_process_name$ spawning $process_name$ was identified
on endpoint $dest$ by user $user$ attempting to encrypt disks.
mitre_attack_id:
- T1486
observable:
- name: user
type: User
role:
- Victim
- name: dest
type: Hostname
role:
- Victim
- name: parent_process_name
type: Process
role:
- Parent Process
- name: process_name
type: Process
role:
- Child Process
product:
- Splunk Enterprise
- Splunk Enterprise Security
- Splunk Cloud
required_fields:
- _time
- Processes.dest
- Processes.user
- Processes.parent_process_name
- Processes.parent_process
- Processes.original_file_name
- Processes.process_name
- Processes.process
- Processes.process_id
- Processes.parent_process_path
- Processes.process_path
- Processes.parent_process_id
risk_score: 35
security_domain: endpoint
tests:
- name: True Positive Test
attack_data:
- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1486/dcrypt/windows-sysmon.log
source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
sourcetype: xmlwineventlog