Windows Process CommandLine contains -export dll_u (DLL export function load)

Flags Windows processes that invoke a DLL export function named dll_u via command-line export arguments.

FreeReviewedSigma · Critical · v5

Product: windows
Category: process_creation
Author: Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2019-03-04
Updated: 2026-07-31

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 matches Windows process command lines that include the DLL export function name "dll_u" via the "-export" parameter. Attackers may use DLL export function invocation patterns to load or execute code in a stealthy way, blending into legitimate-looking command-line activity. Detection relies on process creation telemetry with the full CommandLine field.

Reporting behind it

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Windows Process CommandLine contains -export dll_u (DLL export function load)

Pivot detection · T1218.011 · 9 related

Changelog

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
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-process-creation-export-dll-u-or-trailing-dll-u-in-commandline-d465d1d8

title: Windows Process CommandLine contains -export dll_u (DLL export function load)
id: 0c6c6b27-c300-4a59-8735-d03729700f0c
status: stable
description: This rule matches Windows process command lines that include the DLL export function name "dll_u" via the "-export" parameter. Attackers may use DLL export function invocation patterns to load or execute code in a stealthy way, blending into legitimate-looking command-line activity. Detection relies on process creation telemetry with the full CommandLine field.
references:
  - https://github.com/00derp/EquationGroupLeak/search?utf8=%E2%9C%93&q=dll_u&type=
  - https://twitter.com/cyb3rops/status/972186477512839170
  - https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2019/TA/EquationGroup/proc_creation_win_apt_equationgroup_dll_u_load.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2019-03-04
modified: 2023-03-09
tags:
  - attack.stealth
  - attack.g0020
  - attack.t1218.011
  - detection.emerging-threats
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    - CommandLine|contains: -export dll_u
    - CommandLine|endswith:
        - ",dll_u"
        - " dll_u"
  condition: selection
falsepositives:
  - Unlikely
level: critical
license: DRL-1.1
related:
  - id: d465d1d8-27a2-4cca-9621-a800f37cf72e
    type: derived

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