FortiSIEM Rules

Windows: Suspicious Rundll32 Setupapi.dll Activity

Rule ID


Default Status



setupapi.dll library provide InstallHinfSection function for processing INF files. INF file may contain instructions allowing to create values in the registry, modify files and install drivers. This technique could be used to obtain persistence via modifying one of Run or RunOnce registry keys, run process or use other DLLs chain calls (see references) InstallHinfSection function in setupapi.dll calls runonce.exe executable regardless of actual content of INF file. This rule is adapted from






Defense Evasion

Defense Evasion consists of techniques that adversaries use to avoid detection throughout their compromise. Techniques used for defense evasion include uninstalling/disabling security software or obfuscating/encrypting data and scripts. Adversaries also leverage and abuse trusted processes to hide and masquerade their malware. Other tactics’ techniques are cross-listed here when those techniques include the added benefit of subverting defenses.

MITRE ATT&CK® Techniques


Signed Binary Proxy Execution: Rundll32

Adversaries may abuse rundll32.exe to proxy execution of malicious code. Rundll32.exe is commonly associated with executing DLL payloads. However, Rundll32.exe can also be used to execute Control Panel Item files (.cpl) through the undocumented shell32.dll functions.



Data Source

Windows Sysmon via FortiSIEM Agent



Remediation Guidance

No remediation guidance specified

Time Window

If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.

300 seconds

Trigger Conditions

If the following defined pattern/s occur within a 300 second time window.


SubPattern Definitions

SubPattern Name: Filter

This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.

SubPattern Query

This is the query logic that matches incoming events

eventType="Win-Sysmon-1-Create-Process" AND procName REGEXP "\\runonce\.exe$" AND parentProcName REGEXP "\\rundll32\.exe$" AND parentCommand REGEXP ".*setupapi\.dll.*" AND parentCommand REGEXP ".*InstallHinfSection.*"

Group by Attributes

This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID


Aggregate Constraint

This is most typically a numerical constraint that defines when the rule should trigger an incident

COUNT(*) >= 1

Incident Attribute Mapping

This section defines which fields in matching raw events should be mapped to the incident attributes in the resulting incident.

The available raw event attributes to map are limited to the group by attributes and the aggregate event constraint fields for each subpattern

hostName = Filter.hostName,
parentCommand = Filter.parentCommand,
parentProcName = Filter.parentProcName,
procName = Filter.procName