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Description

This search looks for execution of process outlook.exe where the process is writing a .zip file to the disk.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel:
  • Last Updated: 2020-07-21
  • Author: Bhavin Patel, Splunk
  • ID: a51bfe1a-94f0-4822-b1e4-16ae10145893

ATT&CK

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

| tstats `security_content_summariesonly`  min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes where Processes.process_name=outlook.exe OR Processes.process_name=explorer.exe by _time span=5m Processes.parent_process_id Processes.process_id Processes.dest Processes.process_name Processes.parent_process_name Processes.user 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| rename process_id as malicious_id
| rename parent_process_id as outlook_id
| join malicious_id type=inner[
| tstats `security_content_summariesonly` count values(Filesystem.file_path) as file_path values(Filesystem.file_name) as file_name  FROM datamodel=Endpoint.Filesystem where (Filesystem.file_path=*zip*   OR Filesystem.file_name=*.lnk ) AND (Filesystem.file_path=C:\\Users* OR Filesystem.file_path=*Local\\Temp*) by  _time span=5m Filesystem.process_id Filesystem.file_hash Filesystem.dest  
| `drop_dm_object_name(Filesystem)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| rename process_id as malicious_id
| fields malicious_id outlook_id dest file_path file_name file_hash count file_id] 
| table firstTime lastTime user malicious_id outlook_id process_name parent_process_name file_name  file_path 
| where file_name != "" 
| `detect_outlook_exe_writing_a_zip_file_filter` 

Associated Analytic Story

How To Implement

You must be ingesting data that records filesystem and process activity from your hosts to populate the Endpoint data model. This is typically populated via endpoint detection-and-response product, such as Carbon Black, or endpoint data sources, such as Sysmon.

Required field

  • _time
  • Processes.process_name
  • Processes.parent_process_id
  • Processes.process_id
  • Processes.dest
  • Processes.parent_process_name
  • Processes.user

Kill Chain Phase

  • Installation
  • Actions on Objectives

Known False Positives

It is not uncommon for outlook to write legitimate zip files to the disk.

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: 3