Detection: Resize Shadowstorage Volume

Date: 2021-11-30 ID: dbc30554-d27e-11eb-9e5e-acde48001122 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk User Behavior Analytics

Description

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.

Annotations

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Implementation

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

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
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.	64	80	80

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Version: 6