Windows Rundll32 Loads DLL Export StartNodeRelay (F-Secure C3)

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1218.011Rundll32
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule identifies process creation where rundll32.exe is invoked with a DLL that includes the StartNodeRelay export. Adversaries can use rundll32-based DLL loading to execute code in a way that may blend with normal Windows process behavior. The detection relies on command-line telemetry containing rundll32.exe, a referenced .dll file, and the StartNodeRelay string.

Reporting behind it

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Suspicious Rundll32 Executing DLL Start Export With Control Flags

Windows Rundll32 Loads DLL Export StartNodeRelay (F-Secure C3)

Pivot detection · T1218.011 · 9 related

Changelog

v2

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-rundll32-execution-loading-dlls-exported-with-startnoderelay-b18c9d4c

title: Windows Rundll32 Loads DLL Export StartNodeRelay (F-Secure C3)
id: 8bd15a2a-81f1-4619-ad21-ecac1de2859b
status: test
description: This rule identifies process creation where rundll32.exe is invoked with a DLL that includes the StartNodeRelay export. Adversaries can use rundll32-based DLL loading to execute code in a way that may blend with normal Windows process behavior. The detection relies on command-line telemetry containing rundll32.exe, a referenced .dll file, and the StartNodeRelay string.
references:
  - https://github.com/FSecureLABS/C3/blob/11a081fd3be2aaf2a879f6b6e9a96ecdd24966ef/Src/NodeRelayDll/NodeRelayDll.cpp#L12
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_hktl_c3_rundll32_pattern.yml
author: Alfie Champion (ajpc500), Huntrule Team
date: 2021-06-02
modified: 2023-03-05
tags:
  - attack.stealth
  - attack.t1218.011
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    CommandLine|contains|all:
      - rundll32.exe
      - .dll
      - StartNodeRelay
  condition: selection
falsepositives:
  - Unknown
level: critical
license: DRL-1.1
related:
  - id: b18c9d4c-fac9-4708-bd06-dd5bfacf200f
    type: derived

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