Detection: Windows AppLocker Block Events

Updated Date: 2024-05-15 ID: e369afe8-cd35-47a3-9c1e-d813efc1f7dd Author: Michael Haag, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects attempts to bypass application restrictions by identifying Windows AppLocker policy violations. It leverages Windows AppLocker event logs, specifically EventCodes 8007, 8004, 8022, 8025, 8029, and 8040, to pinpoint blocked actions. This activity is significant for a SOC as it highlights potential unauthorized application executions, which could indicate malicious intent or policy circumvention. If confirmed malicious, this activity could allow an attacker to execute unauthorized applications, potentially leading to further system compromise or data exfiltration.

1`applocker`  EventCode IN (8007, 8004, 8022, 8025, 8029, 8040) 
2| spath input=UserData_Xml 
3| rename RuleAndFileData.* as *, TargetUser as user, Computer as dest  
4| stats count min(_time) as firstTime max(_time) as lastTime by dest, PolicyName, RuleId, user, TargetProcessId, FilePath, FullFilePath, EventCode 
5| lookup applockereventcodes EventCode OUTPUT Description 
6| `security_content_ctime(firstTime)` 
7| `security_content_ctime(lastTime)` 
8| `windows_applocker_block_events_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_block_events_filter search *
windows_applocker_block_events_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 True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

To implement this analytic, you must be ingesting Windows AppLocker logs into Splunk. Ensure proper logging is setup for AppLocker and data is being ingested into Splunk.

Known False Positives

Administrators may legitimately use AppLocker to allow applications.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
An instance of AppLocker policy violation has been detected on $dest$. 16 20 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 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: 3