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Description

The following analytic identifies when a suspicious email is detected within the Microsoft Office 365 ecosystem through the Advanced Threat Protection engine and delivered to an end user. Attackers may execute several attacks through email, any detections from built-in Office 365 capabilities should be monitored and responded to appropriately. Certain premium Office 365 capabilities such as Safe Attachment and Safe Links further enhance these detection and response functions.

  • Type: Anomaly

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-04-01
  • Author: Steven Dick
  • ID: 605cc93a-70e4-4ee3-9a3d-1a62e8c9b6c2

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1566 Phishing Initial Access
T1566.001 Spearphishing Attachment Initial Access
T1566.002 Spearphishing Link Initial Access
Kill Chain Phase
  • Delivery
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`o365_management_activity` Workload=ThreatIntelligence Operation=TIMailData DeliveryAction!=Blocked Directionality=InBound 
| rename P2Sender as src_user, P1Sender as sender, Recipients{} as user, DeliveryAction as action 
| stats values(SenderIp) as src, values(Subject) as subject, values(user) as user, values(action) as action, values(SystemOverrides{}.Details) as reason, values(LatestDeliveryLocation) as result, values(ThreatsAndDetectionTech{}) as category, values(AttachmentData{}.FileName) as file_name, values(AttachmentData{}.FileType) as file_type, values(AttachmentData{}.SHA256) as file_hash values(DetectionMethod) as signature, min(_time) as firstTime max(_time) as lastTime, count  by src_user,sender 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `o365_threat_intelligence_suspicious_email_delivered_filter`

Macros

The SPL above uses the following Macros:

:information_source: o365_threat_intelligence_suspicious_email_delivered_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
  • P2Sender
  • P1Sender
  • Recipients
  • DeliveryAction
  • Operation
  • Workload

How To Implement

You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. The threat intelligence workload is typically only visible to E3/E5 level customers.

Known False Positives

unknown

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
20.0 20 100 A suspicious email was delivered to $user$ by $src_user$ matching the $signature$ 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