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Description

This search is to detect a suspicious MS office application that drop or create executables or script in the host. This behavior is commonly seen in spear phishing office attachment where it drop malicious files or script to compromised the host. It might be some normal macro may drop script or tools as part of automation but still this behavior is reallly suspicious and not commonly seen in normal office application

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-09-13
  • Author: Teoderick Contreras, Michael Haag Splunk
  • ID: 73ce70c4-146d-11ec-9184-acde48001122

ATT&CK

ID Technique Tactic
T1566 Phishing Initial Access
T1566.001 Spearphishing Attachment Initial Access

| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name IN ("winword.exe","excel.exe","powerpnt.exe","mspub.exe","visio.exe","wordpad.exe","wordview.exe") by _time span=1h Processes.process_id Processes.process_name Processes.process Processes.dest Processes.process_guid 
| `drop_dm_object_name(Processes)` 
|rename process_guid as proc_guid 
|join proc_guid, _time [
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.exe","*.dll","*.pif","*.scr","*.js","*.vbs","*.vbe","*.ps1") by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.process_guid Filesystem.file_path 
| `drop_dm_object_name(Filesystem)` 
| rename process_guid as proc_guid 
| fields _time dest file_create_time file_name file_path process_name process_path process proc_guid] 
| dedup file_create_time 
| table dest, process_name, process, file_create_time, file_name, file_path, proc_guid 
| `office_application_drop_executable_filter`

Associated Analytic Story

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. Tune and filter known instances where renamed rundll32.exe may be used.

Required field

  • _time
  • Image
  • TargetFilename
  • ProcessGuid
  • dest
  • user_id

Kill Chain Phase

  • Exploitation

Known False Positives

office macro for automation may do this behavior

RBA

Risk Score Impact Confidence Message
64.0 80 80 process $process_name$ drops a file $TargetFilename$ in host $dest$

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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