Detection: Windows Audit Policy Excluded Category via Auditpol

Description

The following analytic identifies the execution of auditpol.exe with the "/set" and "/exclude" command-line arguments which indicates that the user's per-user policy will cause audit to be suppressed regardless of the system audit policy. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line executions. This activity can be significant as it indicates potential defense evasion by adversaries or Red Teams, aiming to exclude specific users events from log data. If confirmed malicious, this behavior could allow attackers to bypass defenses, and plan further attacks, potentially leading to full machine compromise or lateral movement.

Search

 1
 2| tstats `security_content_summariesonly` values(Processes.process) as process min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
 3  WHERE `process_auditpol` Processes.process="*/set*" Processes.process="*/exclude*"
 4    AND
 5    NOT Processes.process="*/?*"
 6  BY Processes.action Processes.dest Processes.original_file_name
 7     Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
 8     Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
 9     Processes.process Processes.process_exec Processes.process_guid
10     Processes.process_hash Processes.process_id Processes.process_integrity_level
11     Processes.process_name Processes.process_path Processes.user
12     Processes.user_id Processes.vendor_product
13
14| `drop_dm_object_name(Processes)`
15
16| `security_content_ctime(firstTime)`
17
18| `security_content_ctime(lastTime)`
19
20| `windows_audit_policy_excluded_category_via_auditpol_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	Other	'crowdstrike:events:sensor'	'crowdstrike'
Sysmon EventID 1	Windows	'XmlWinEventLog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688	Windows	'XmlWinEventLog'	'XmlWinEventLog:Security'

Macros Used

Annotations

Default Configuration

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

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process name, and process original file name. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

False positives should be rare, investigate the activity, and apply additional filters when necessary.

Associated Analytic Story

• Windows Audit Policy Tampering

Intermediate Findings

Threat Objects

References

• https://attack.mitre.org/techniques/T1562/002/

• https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/auditpol-set

• https://www.microsoft.com/en-us/security/blog/2021/01/20/deep-dive-into-the-solorigate-second-stage-activation-from-sunburst-to-teardrop-and-raindrop/

• https://www.cybereason.com/blog/research/prometei-botnet-exploiting-microsoft-exchange-vulnerabilities

Detection Testing

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: 8