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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

| 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

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

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

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