The following analytic identifies the resizing of shadowstorage using vssadmin.exe to avoid the shadow volumes being made again. This technique is typically found used by adversaries during a ransomware event and a precursor to deleting the shadowstorage.
- Type: TTP
Product: Splunk Behavioral Analytics
- Last Updated: 2021-11-30
- Author: Teoderick Contreras, Splunk
- ID: dbc30554-d27e-11eb-9e5e-acde48001122
Kill Chain Phase
- Actions On Objectives
- CIS 10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 $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_cmd_line LIKE "%shadowstorage%" AND process_cmd_line LIKE "%resize%" AND process_cmd_line LIKE "%maxsize%" AND process_file_name="vssadmin.exe" --finding_report--
The SPL above uses the following Macros:
resize_shadowstorage_volume_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
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.
Known False Positives
System administrators may resize the shadowstorage for valid purposes. Filter as needed.
Associated Analytic Story
|64.0||80||80||An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest_device_id$ by user $dest_user_id$ attempting to create a shadow copy to perform offline password cracking.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 3