Detection: O365 DLP Rule Triggered

Updated Date: 2024-04-01 ID: 63a8a537-36fd-4aac-a3ea-1a96afd2c871 Author: Steven Dick Type: Anomaly Product: Splunk Enterprise Security

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.

1`o365_management_activity` Operation=DLPRuleMatch 
2| 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') 
3| 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 
4| `o365_dlp_rule_triggered_filter` 
5| stats count min(firstTime) as firstTime max(lastTime) as lastTime values(*) AS * by src_user,signature_id 
6| eval action = CASE(match(result,"Halt"),"blocked",isnotnull(result),"alert",true(),"allow") 
7|`security_content_ctime(firstTime)`  
8|`security_content_ctime(lastTime)`

Data Source

Name Platform Sourcetype Source Supported App
N/A N/A N/A N/A N/A

Macros Used

Name Value
o365_management_activity sourcetype=o365:management:activity
o365_dlp_rule_triggered_filter search *
o365_dlp_rule_triggered_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1048 Exfiltration Over Alternative Protocol Exfiltration
T1567 Exfiltration Over Web Service Exfiltration
KillChainPhase.ACTIONS_ON_OBJECTIVES
NistCategory.DE_AE
Cis18Value.CIS_10
TeamTNT
APT28
Magic Hound

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
User $src_user$ triggered a Microsoft Office DLP rule. 20 40 50
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset o365 o365:management:activity
Integration ✅ Passing Dataset o365 o365:management:activity

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: GitHub | Version: 1