Detection: Windows AppLocker Rare Application Launch Detection

Updated Date: 2024-05-30 ID: 9556f7b7-285f-4f18-8eeb-963d989f9d27 Author: Michael Haag, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic detects the launch of rarely used applications within the environment, which may indicate the use of potentially malicious software or tools by attackers. It leverages Windows AppLocker event logs, aggregating application launch counts over time and flagging those that significantly deviate from the norm. This behavior is significant as it helps identify unusual application activity that could signal a security threat. If confirmed malicious, this activity could allow attackers to execute unauthorized code, potentially leading to further compromise of the system.

1`applocker` 
2| spath input=UserData_Xml 
3| rename RuleAndFileData.* as *, Computer as dest, TargetUser AS user 
4| stats dc(_time) as days, count by FullFilePath dest user 
5| eventstats avg(count) as avg, stdev(count) as stdev 
6| eval upperBound=(avg+stdev*3), lowerBound=(avg-stdev*3) 
7| where count > upperBound OR count < lowerBound 
8| `windows_applocker_rare_application_launch_detection_filter`

Data Source

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

Macros Used

Name Value
applocker (source="WinEventLog:Microsoft-Windows-AppLocker/*" OR source="XmlWinEventLog:Microsoft-Windows-AppLocker/*")
windows_applocker_rare_application_launch_detection_filter search *
windows_applocker_rare_application_launch_detection_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
T1218 System Binary Proxy Execution Defense Evasion
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
Lazarus Group

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 False
This configuration file applies to all detections of type hunting.

Implementation

The analytic is designed to be run against Windows AppLocker event logs collected from endpoints with AppLocker enabled. If using Microsoft Defender for Endpoint (MDE), modify the analytic to use EventTypes/ActionTypes that match the block events for AppLocker. The analytic requires the AppLocker event logs to be ingested into Splunk. Note that, an additional method to reduce any false positives would be to add the specific EventCodes - 8003 or 8004 and filter from there.

Known False Positives

False positives are possible if legitimate users are launching applications that are not permitted by AppLocker. It is recommended to investigate the context of the application launch to determine if it is malicious or not. Modify the threshold as needed to reduce false positives.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
An application launch that deviates from the norm was detected on a host $dest$. 15 50 30
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-AppLocker/MSI and Script xmlwineventlog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-AppLocker/MSI and Script 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: 2