Resize ShadowStorage volume

name: Resize ShadowStorage volume
id: bc760ca6-8336-11eb-bcbb-acde48001122
version: 9
date: '2026-03-10'
author: Teoderick Contreras
status: production
type: TTP
description: The following analytic identifies the resizing of shadow storage volumes, a technique used by ransomware like CLOP to prevent the recreation of shadow volumes. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions involving "vssadmin.exe" with parameters related to resizing shadow storage. This activity is significant as it indicates an attempt to hinder recovery efforts by manipulating shadow copies. If confirmed malicious, this could lead to successful ransomware deployment, making data recovery difficult and increasing the potential for data loss.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
search: |-
    | tstats `security_content_summariesonly` values(Processes.process) as cmdline values(Processes.parent_process_name) as parent_process values(Processes.process_name) as process_name min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
      WHERE Processes.parent_process_name = "cmd.exe"
        OR
        Processes.parent_process_name = "powershell.exe"
        OR
        Processes.parent_process_name = "powershell_ise.exe"
        OR
        Processes.parent_process_name =  "wmic.exe" Processes.process_name = "vssadmin.exe" Processes.process="*resize*" Processes.process="*shadowstorage*" Processes.process="*/maxsize*"
      BY Processes.action Processes.dest Processes.original_file_name
         Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
         Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
         Processes.process Processes.process_exec Processes.process_guid
         Processes.process_hash Processes.process_id Processes.process_integrity_level
         Processes.process_name Processes.process_path Processes.user
         Processes.user_id Processes.vendor_product
    | `drop_dm_object_name(Processes)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `resize_shadowstorage_volume_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: network admin can resize the shadowstorage for valid purposes.
references:
    - https://www.mandiant.com/resources/fin11-email-campaigns-precursor-for-ransomware-data-theft
    - https://blog.virustotal.com/2020/11/keep-your-friends-close-keep-ransomware.html
    - https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1490/T1490.md
    - https://redcanary.com/blog/blackbyte-ransomware/
    - https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/vssadmin-resize-shadowstorage
drilldown_searches:
    - name: View the detection results for - "$dest$" and "$user$"
      search: '%original_detection_search% | search  dest = "$dest$" user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$" and "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$", "$user$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: A process $parent_process_name$ attempted to resize shadow copy with commandline $process$ in host $dest$
    risk_objects:
        - field: dest
          type: system
          score: 50
        - field: user
          type: user
          score: 50
    threat_objects: []
tags:
    analytic_story:
        - Medusa Ransomware
        - Clop Ransomware
        - Compromised Windows Host
        - BlackByte Ransomware
        - VanHelsing Ransomware
    asset_type: Endpoint
    mitre_attack_id:
        - T1490
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/clop/clop_a/windows-sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog