Try in Splunk Security Cloud

Description

This search is to detect a shared file in google drive with suspicious file name that are commonly used by spear phishing campaign. This technique is very popular to lure the user by running a malicious document or click a malicious link within the shared file that will redirected to malicious website. This detection can also catch some normal email communication between organization and its external customer.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud, Dev Sec Ops Analytics
  • Datamodel:
  • Last Updated: 2021-08-23
  • Author: Teoderick Contreras, Splunk
  • ID: 07eed200-03f5-11ec-98fb-acde48001122

ATT&CK

ID Technique Tactic
T1566.001 Spearphishing Attachment Initial Access
`gsuite_drive` parameters.owner_is_team_drive=false "parameters.doc_title" IN ("*dhl*", "* ups *", "*delivery*", "*parcel*", "*label*", "*invoice*", "*postal*", "*fedex*", "* usps *", "* express *", "*shipment*", "*Banking/Tax*","*shipment*", "*new order*") parameters.doc_type IN ("document","pdf", "msexcel", "msword", "spreadsheet", "presentation") 
| rex field=parameters.owner "[^@]+@(?<source_domain>[^@]+)" 
| rex field=parameters.target_user "[^@]+@(?<dest_domain>[^@]+)" 
| where not source_domain="internal_test_email.com" and dest_domain="internal_test_email.com" 
| eval phase="plan" 
| eval severity="low" 
| stats count min(_time) as firstTime max(_time) as lastTime by email parameters.owner parameters.target_user parameters.doc_title parameters.doc_type phase severity 
| rename parameters.target_user AS user 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `gsuite_suspicious_shared_file_name_filter`

Associated Analytic Story

How To Implement

To successfully implement this search, you need to be ingesting logs related to gsuite having the file attachment metadata like file type, file extension, source email, destination email, num of attachment and etc.

Required field

  • _time
  • parameters.doc_title
  • src_domain
  • dest_domain
  • email
  • parameters.visibility
  • parameters.owner
  • parameters.doc_type

Kill Chain Phase

  • Exploitation

Known False Positives

normal user or normal transaction may contain the subject and file type attachment that this detection try to search

RBA

Risk Score Impact Confidence Message
21.0 30 70 suspicious share gdrive from $parameters.owner$ to $email$ namely as $parameters.doc_title$

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