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Description

The following analytics identifies the resizing of shadowstorage by ransomware malware to avoid the shadow volumes being made again. this technique is an alternative by ransomware attacker than deleting the shadowstorage which is known alert in defensive team. one example of ransomware that use this technique is CLOP ransomware where it drops a .bat file that will resize the shadowstorage to minimum size as much as possible

  • Type: TTP
  • Product: Splunk Behavioral Analytics
  • Datamodel: Endpoint
  • Last Updated: 2021-06-21
  • Author: Teoderick Contreras, Splunk
  • ID: dbc30554-d27e-11eb-9e5e-acde48001122

ATT&CK

ID Technique Tactic
T1489 Service Stop Impact 

| from read_ssa_enriched_events() 
| eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)), cmd_line=lower(ucast(map_get(input_event, "process"), "string", null)), process_name=lower(ucast(map_get(input_event, "process_name"), "string", null)), process_path=ucast(map_get(input_event, "process_path"), "string", null), parent_process_name=ucast(map_get(input_event, "parent_process_name"), "string", null), event_id=ucast(map_get(input_event, "event_id"), "string", null) 
| where cmd_line IS NOT NULL AND like(cmd_line, "%resize%") AND like(cmd_line, "%shadowstorage%") AND like(cmd_line, "%maxsize%") AND process_name="vssadmin.exe" 
| eval start_time=timestamp, end_time=timestamp, entities=mvappend(ucast(map_get(input_event, "dest_user_id"), "string", null), ucast(map_get(input_event, "dest_device_id"), "string", null)), body=create_map(["event_id", event_id, "cmd_line", cmd_line, "process_name", process_name, "parent_process_name", parent_process_name, "process_path", process_path]) 
| into write_ssa_detected_events();

Associated Analytic Story

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Required field

  • _time
  • dest_device_id
  • process_name
  • parent_process_name
  • process_path
  • dest_user_id
  • process

Kill Chain Phase

  • Exploitation

Known False Positives

network admin can resize the shadowstorage for valid purposes.

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: 2