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Description

This search can help the detection of compromised accounts or internal users sending suspcious calendar invites via GSuite calendar. These invites may contain malicious links or attachments.

  • Type: Hunting
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel:
  • Last Updated: 2021-10-24
  • Author: Rod Soto, Teoderick Contreras
  • ID: 03cdd68a-34fb-11ec-9bd3-acde48001122

ATT&CK

ID Technique Tactic
T1566 Phishing Initial Access
`gsuite_calendar` 
|bin span=5m _time 
|rename parameters.* as * 
|search target_calendar_id!=null email="*yourdomain.com"
| stats  count values(target_calendar_id) values(event_title) values(event_guest) by email _time 
| where count >100
| `gsuite_suspicious_calendar_invite_filter`

Associated Analytic Story

How To Implement

In order to successfully implement this search, you need to be ingesting logs related to gsuite (gsuite:calendar:json) having the file sharing metadata like file type, source owner, destination target user, description, etc. This search can also be made more specific by selecting specific emails, subdomains timeframe, organizational units, targeted user, etc. In order for the search to work for your environment please update yourdomain.com value in the query with the domain relavant for your organization.

Required field

  • _time
  • email
  • parameters.event_title
  • parameters.target_calendar_id
  • parameters.event_title

Kill Chain Phase

  • Exploitation

Known False Positives

This search will also produce normal activity statistics. Fields such as email, ip address, name, parameters.organizer_calendar_id, parameters.target_calendar_id and parameters.event_title may give away phishing intent.For more specific results use email parameter.

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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