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.

Techniques

T1218

Sample rules

Windows AppLocker Rare Application Launch Detection

source: splunk
technicques:
- T1218

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.

Detection logic

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