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Description

The following analytic identifies instances where the O365 advanced audit is disabled for a specific user within the Office 365 tenant. It leverages O365 audit logs, specifically events related to audit license changes or modifications within the AzureActiveDirectory workloads. The O365 advanced audit provides granular logging and insights into user and administrator activities, making it a crucial tool for security monitoring and incident response. Disabling this audit for a user can blind security teams to potential malicious or unauthorized activities related to that user's mailbox or account. Attackers may disable these audits to obscure their actions and reduce the chances of detection. If an attacker successfully disables the O365 advanced audit for a user, they can operate within that user's mailbox or account with reduced risk of detection. This can lead to unauthorized data access, data exfiltration, account compromise, or other malicious activities without leaving a detailed audit trail.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Change
  • Last Updated: 2023-09-19
  • Author: Mauricio Velazco, Michael Haag, Splunk
  • ID: 49862dd4-9cb2-4c48-a542-8c8a588d9361

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1562 Impair Defenses Defense Evasion
T1562.008 Disable or Modify Cloud Logs Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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

Macros

The SPL above uses the following Macros:

:information_source: o365_advanced_audit_disabled_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
  • ExtendedProperties{}.Name
  • ExtendedProperties{}.Value
  • user
  • object

How To Implement

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

RBA

Risk Score Impact Confidence Message
32.0 40 80 Advanced auditing for user $object$ was disabled by $user$

: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