Detection: Windows Admin Permission Discovery

Updated Date: 2024-09-30 ID: e08620cb-9488-4052-832d-97bcc0afd414 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic identifies the creation of a suspicious file named 'win.dat' in the root directory (C:). It leverages data from the Endpoint.Filesystem datamodel to detect this activity. This behavior is significant as it is commonly used by malware like NjRAT to check for administrative privileges on a compromised host. If confirmed malicious, this activity could indicate that the malware has administrative access, allowing it to perform high-privilege actions, potentially leading to further system compromise and persistence.

 1
 2|tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.exe", "*.dll", "*.sys", "*.com", "*.vbs", "*.vbe", "*.js", "*.bat", "*.cmd", "*.pif", "*.lnk", "*.dat") by Filesystem.dest Filesystem.file_create_time Filesystem.process_id Filesystem.process_guid Filesystem.file_name Filesystem.file_path Filesystem.user 
 3| `drop_dm_object_name(Filesystem)` 
 4| eval dropped_file_path = split(file_path, "\\") 
 5| eval dropped_file_path_split_count = mvcount(dropped_file_path) 
 6| eval root_drive = mvindex(dropped_file_path,0) 
 7| where LIKE(root_drive, "C:") AND dropped_file_path_split_count = 2 
 8| `security_content_ctime(firstTime)` 
 9| `security_content_ctime(lastTime)` 
10| `windows_admin_permission_discovery_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 11 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_admin_permission_discovery_filter search *
windows_admin_permission_discovery_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
T1069.001 Local Groups Discovery
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
Chimera
HEXANE
OilRig
Tonto Team
Turla
Volt Typhoon
admin@338

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

To successfully implement this search you need to be ingesting information on process that include the name of the Filesystem responsible for the changes from your endpoints into the Endpoint datamodel in the Filesystem node.

Known False Positives

False positives may occur if there are legitimate accounts with the privilege to drop files in the root of the C drive. It's recommended to verify the legitimacy of such actions and the accounts involved.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
A file was created in root drive C:/ on host - $dest$ 25 50 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 XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog

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