splunk-security_content/docs/_posts/2021-11-15-windows_diskcryptor_usage.md

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

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Windows DiskCryptor Usage	Data Encrypted for Impact	Endpoint	2021-11-15	true		Data Encrypted for Impact Impact Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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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.

• Type: Hunting
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2021-11-15
• Author: Michael Haag, Splunk
• ID: d56fe0c8-4650-11ec-a8fa-acde48001122

ATT&CK

ID	Technique	Tactic
T1486	Data Encrypted for Impact	Impact

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`

Associated Analytic Story

• Ransomware

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Required field

• _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

Kill Chain Phase

• Exploitation

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.

RBA

Risk Score	Impact	Confidence	Message
35.0	70	50	An instance of parent_process_name spawning process_name was identified on endpoint dest by user user attempting to encrypt disks.

Reference

• https://thedfirreport.com/2021/11/15/exchange-exploit-leads-to-domain-wide-ransomware/
• https://github.com/DavidXanatos/DiskCryptor

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/T1486/dcrypt/windows-sysmon.log

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