Detection: O365 Advanced Audit Disabled

Updated Date: 2024-09-30 ID: 49862dd4-9cb2-4c48-a542-8c8a588d9361 Author: Mauricio Velazco, Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects instances where the O365 advanced audit is disabled for a specific user within the Office 365 tenant. It uses O365 audit logs, focusing on events related to audit license changes in AzureActiveDirectory workloads. This activity is significant because the O365 advanced audit provides critical logging and insights into user and administrator activities. Disabling it can blind security teams to potential malicious actions. If confirmed malicious, attackers could operate within the user's mailbox or account with reduced risk of detection, leading to unauthorized data access, data exfiltration, or account compromise.

Search

 1`o365_management_activity` Operation="Change user license."  
 2| eval property_name = mvindex ('ExtendedProperties{}.Name', 1) 
 3| search property_name = "extendedAuditEventCategory" 
 4| eval additionalDetails = mvindex('ExtendedProperties{}.Value',0) 
 5| eval split_value=split(additionalDetails, "NewValue") 
 6| eval possible_plan=mvindex(split_value, 1)  
 7| rex field="possible_plan" "DisabledPlans=\[(?P<DisabledPlans>[^\]]+)\]" 
 8| search DisabledPlans IN ("*M365_ADVANCED_AUDITING*") 
 9| stats min(_time) as firstTime max(_time) as lastTime by Operation user object DisabledPlans 
10| `security_content_ctime(firstTime)`  
11| `security_content_ctime(lastTime)` 
12| `o365_advanced_audit_disabled_filter`

Data Source

Name	Platform	Sourcetype	Source
O365 Change user license.	N/A	`'o365:management:activity'`	`'o365'`

Macros Used

Name	Value
o365_management_activity	`sourcetype=o365:management:activity`
o365_advanced_audit_disabled_filter	`search *`

o365_advanced_audit_disabled_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
T1562	Impair Defenses	Defense Evasion
T1562.008	Disable or Modify Cloud Logs	Defense Evasion

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

Magic Hound

APT29

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 Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.

Known False Positives

Administrators might temporarily disable the advanced audit for troubleshooting, performance reasons, or other administrative tasks. Filter as needed.

Associated Analytic Story

Office 365 Persistence Mechanisms

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Advanced auditing for user $object$ was disabled by $user$	32	40	80

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: 3