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Description

The following analytic detects when Microsoft Office 365 Data Loss Prevention (DLP) rules have been triggered. DLP rules can be configured for any number of security, regulatory, or business compliance reasons, as such this analytic will only be as accurate as the upstream DLP configuration. Detections from this analytic should be evaluated thoroughly to determine what, if any, security relevance the underlying DLP events contain.

  • Type: Anomaly

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

  • Last Updated: 2024-04-01
  • Author: Steven Dick
  • ID: 63a8a537-36fd-4aac-a3ea-1a96afd2c871

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1048 Exfiltration Over Alternative Protocol Exfiltration
T1567 Exfiltration Over Web Service Exfiltration
Kill Chain Phase
  • Actions On Objectives
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`o365_management_activity` Operation=DLPRuleMatch 
| eval recipient = 'ExchangeMetaData.To{}', signature_id = 'ExchangeMetaData.UniqueID', signature = 'PolicyDetails{}.Rules{}.RuleName' , src_user = UserId, reason ='PolicyDetails{}.Rules{}.ConditionsMatched.SensitiveInformation{}.SensitiveInformationTypeName', result='PolicyDetails{}.Rules{}.Actions{}', file_name=case(NOT match('PolicyDetails{}.Rules{}.ConditionsMatched.SensitiveInformation{}.Location',"Message Body"),'PolicyDetails{}.Rules{}.ConditionsMatched.SensitiveInformation{}.Location') 
| stats min(_time) as firstTime max(_time) as lastTime values(signature) as signature values(file_name) as file_name values(ExchangeMetaData.Subject) AS subject values(Workload) as app values(result) as result by src_user,recipient,signature_id,reason 
| `o365_dlp_rule_triggered_filter` 
| stats count min(firstTime) as firstTime max(lastTime) as lastTime values(*) AS * by src_user,signature_id 
| eval action = CASE(match(result,"Halt"),"blocked",isnotnull(result),"alert",true(),"allow") 
|`security_content_ctime(firstTime)`  
|`security_content_ctime(lastTime)`

Macros

The SPL above uses the following Macros:

:information_source: o365_dlp_rule_triggered_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
  • Operation
  • ExchangeMetaData.To{}
  • ExchangeMetaData.UniqueID
  • PolicyDetails{}.Rules{}.RuleName
  • UserId
  • PolicyDetails{}.Rules{}.ConditionsMatched.SensitiveInformation{}.SensitiveInformationTypeName
  • PolicyDetails{}.Rules{}.Actions{}
  • PolicyDetails{}.Rules{}.ConditionsMatched.SensitiveInformation{}.Location

How To Implement

You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. You must deploy DLP rules through O365 security and compliance functions.

Known False Positives

WIll depending on accuracy of DLP rules, these can be noisy so tune appropriately.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
20.0 40 50 User $src_user$ triggered a Microsoft Office DLP rule.

: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