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Detection rules › Splunk

O365 DLP Rule Triggered

Status
production
Severity
low
Group by
action, aws::recipientAccountId, dest, reason, recipient, signature_id, src, user, vendor_product
Author
Steven Dick
Source
github.com/splunk/security_content

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 de termine what, if any, security relevance the underlying DLP events contain.

MITRE ATT&CK coverage

TacticTechniques
ExfiltrationT1048 Exfiltration Over Alternative Protocol, T1567 Exfiltration Over Web Service

Rule body splunk

name: O365 DLP Rule Triggered
id: 63a8a537-36fd-4aac-a3ea-1a96afd2c871
version: 10
creation_date: '2024-04-07'
modification_date: '2026-05-13'
author: Steven Dick
status: production
type: Anomaly
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 de termine what, if any, security relevance the underlying DLP events contain.
data_source:
    - Office 365 Universal Audit Log
search: '`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'') | fillnull | stats count 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 action dest user src vendor_account vendor_product src_user recipient signature_id reason | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_dlp_rule_triggered_filter` '
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.
references:
    - https://learn.microsoft.com/en-us/purview/dlp-learn-about-dlp
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: user
          type: user
          score: 20
          message: User $user$ triggered a Microsoft Office DLP rule.
analytic_story:
    - Data Exfiltration
asset_type: O365 Tenant
mitre_attack_id:
    - T1048
    - T1567
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1566/o365_various_alerts/o365_various_alerts.log
          sourcetype: o365:management:activity
          source: o365
      test_type: unit

Stages and Predicates

Stage 1: search

`o365_management_activity` Operation=DLPRuleMatch

Stage 2: eval

| 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')
file_name =
else'PolicyDetails{}.Rules{}.ConditionsMatched.SensitiveInformation{}.Location'

Stage 3: fillnull

| fillnull

Stage 4: stats

| stats count 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 action dest user src vendor_account vendor_product src_user recipient signature_id reason

Stage 5: search

| `security_content_ctime(firstTime)`

Stage 6: search

| `security_content_ctime(lastTime)`

Stage 7: search

| `o365_dlp_rule_triggered_filter`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Operationeq
  • DLPRuleMatch
sourcetypeeq
  • o365:management:activity