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Description

this search is to detect execution of cipher.exe to clear the unallocated sectors of a specific disk. This technique was seen in some ransomware to make it impossible to forensically recover deleted files.

  • Type: TTP

  • Product: Splunk Behavioral Analytics

  • Last Updated: 2021-12-20
  • Author: Teoderick Contreras, Splunk
  • ID: 8f907d90-6173-11ec-9c23-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1070.004 File Deletion Defense Evasion
T1070 Indicator Removal Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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 $main = from source  
| eval timestamp = time  
| eval metadata_uid = metadata.uid  
| eval process_pid = process.pid 
| eval process_file = process.file 
| eval process_file_path = process_file.path 
| eval process_file_name = lower(process_file.name) 
| eval process_cmd_line = process.cmd_line 
| eval actor_user = actor.user 
| eval actor_user_name = actor_user.name 
| eval actor_process = actor.process 
| eval actor_process_pid = actor_process.pid 
| eval actor_process_file = actor_process.file 
| eval actor_process_file_path = actor_process_file.path 
| eval actor_process_file_name = actor_process_file.name 
| eval device_hostname = device.hostname 
| where process_file_name="cipher.exe" AND process_cmd_line LIKE "%/w:%" --finding_report--

Macros

The SPL above uses the following Macros:

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

Required fields

List of fields required to use this analytic.

  • process.pid
  • process.file.path
  • process.file.name
  • process.cmd_line
  • actor.user.name
  • actor.process.pid
  • actor.process.file.path
  • actor.process.file.name
  • device.hostname

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.

Known False Positives

administrator may execute this app to manage disk

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
90.0 90 100 An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ attempting to clear the unallocated sectors of a specific disk.

:information_source: 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

source | version: 4