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Description

This search looks for high frequency of file deletion relative to process name and process id. These events usually happen when the ransomware tries to encrypt the files with the ransomware file extensions and sysmon treat the original files to be deleted as soon it was replace as encrypted data.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-03-16
  • Author: Teoderick Contreras
  • ID: 45b125c4-866f-11eb-a95a-acde48001122

ATT&CK

ID Technique Tactic
T1485 Data Destruction Impact
`sysmon` EventCode=23 TargetFilename IN ("*\.cmd", "*\.ini","*\.gif", "*\.jpg", "*\.jpeg", "*\.db", "*\.ps1", "*\.doc*", "*\.xls*", "*\.ppt*", "*\.bmp","*\.zip", "*\.rar", "*\.7z", "*\.chm", "*\.png", "*\.log", "*\.vbs", "*\.js") 
| stats values(TargetFilename) as deleted_files min(_time) as firstTime max(_time) as lastTime count by Computer user EventCode Image ProcessID 
|where count >=100 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `high_file_deletion_frequency_filter`

Associated Analytic Story

How To Implement

To successfully implement this search, you need to be ingesting logs with the deleted target file name, process name and process id from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Required field

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

Kill Chain Phase

  • Exploitation

Known False Positives

user may delete bunch of pictures or files in a folder.

RBA

Risk Score Impact Confidence Message
72.0 90 80 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

source | version: 1