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Description

The following analytic identifies when one of O365 the built-in security detections for suspicious email behaviors are triggered. These alerts often indicate that an attacker may have compromised a mailbox within the environment. Any detections from built-in Office 365 capabilities should be monitored and responded to appropriately. Certain premium Office 365 capabilities further enhance these detection and response functions.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Email
  • Last Updated: 2024-04-01
  • Author: Steven Dick
  • ID: 85c7555a-05af-4322-81aa-76b4ddf52baa

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1114 Email Collection Collection
T1114.003 Email Forwarding Rule Collection
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`o365_management_activity` Workload=SecurityComplianceCenter Operation=AlertEntityGenerated Name IN ("Suspicious email sending patterns detected","User restricted from sending email","Suspicious Email Forwarding Activity","Email sending limit exceeded") 
| fromjson Data 
| stats count min(_time) as firstTime max(_time) as lastTime by AlertId,ObjectId,Operation,Name 
| rename Name as signature, AlertId as signature_id, ObjectId as user 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `o365_email_suspicious_behavior_alert_filter`

Macros

The SPL above uses the following Macros:

:information_source: o365_email_suspicious_behavior_alert_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • AlertId
  • ObjectId
  • Operation
  • Name
  • Workload

How To Implement

You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. The alerts must be enabled in the o365 security portal.

Known False Positives

Users emailing for legitimate business purposes that appear suspicious.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
90.0 90 100 The user $user$ triggered the O365 security alert [$signature$]

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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