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Description

This analytic will identify excessive file deletion events in the Windows Defender folder. This technique was seen in the WhisperGate malware campaign in which adversaries abused Nirsofts advancedrun.exe to gain administrative privilege to then execute PowerShell commands to delete files within the Windows Defender application folder. This behavior is a good indicator the offending process is trying to corrupt a Windows Defender installation.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2022-01-20
  • Author: Teoderick Contreras, Splunk
  • ID: b5baa09a-7a05-11ec-8da4-acde48001122

Annotations

ATT&CK
ID Technique Tactic
T1485 Data Destruction Impact
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE
1
2
3
4
5
6
`sysmon` EventCode=23 TargetFilename = "*\\ProgramData\\Microsoft\\Windows Defender*" 
| stats values(TargetFilename) as deleted_files min(_time) as firstTime max(_time) as lastTime count by user EventCode Image ProcessID Computer 
|where count >=50 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `excessive_file_deletion_in_windefender_folder_filter`

Macros

The SPL above uses the following Macros:

Note that excessive_file_deletion_in_windefender_folder_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

  • _time
  • EventCode
  • TargetFilename
  • Computer
  • user
  • Image
  • ProcessID

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, TargetFilename, and ProcessID 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

Windows Defender AV updates may cause this alert. Please update the filter macros to remove false positives.

Associated Analytic story

RBA

Risk Score Impact Confidence Message
25.0 50 50 High frequency file deletion activity detected on host $Computer$

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

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