Rundll32 UNC Path Execution

SIGMA detection rule by Nasreddine Bencherchali (Nextron Systems) · NOASSERTION

Detects rundll32 execution where the DLL is located on a remote location (share). Threat actors can abuse the rundll32.exe binary to execute remote DLLs from a UNC pathh.

title: Rundll32 UNC Path Execution
id: 5cdb711b-5740-4fb2-ba88-f7945027afac
status: test
description: |
    Detects rundll32 execution where the DLL is located on a remote location (share).
    Threat actors can abuse the rundll32.exe binary to execute remote DLLs from a UNC pathh.
references:
    - https://www.cybereason.com/blog/rundll32-the-infamous-proxy-for-executing-malicious-code
    - https://www.microsoft.com/en-us/security/blog/2026/07/16/acr-stealer-two-observed-intrusion-chains-amid-increased-threat-activity/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-10
modified: 2026-07-20
tags:
    - attack.execution
    - attack.lateral-movement
    - attack.stealth
    - attack.t1021.002
    - attack.t1218.011
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\rundll32.exe'
        - OriginalFileName: 'RUNDLL32.EXE'
        - CommandLine|contains: 'rundll32'
    selection_cli:
        CommandLine|contains:
            - ' \\\\'
            - ' ''\\\\'
            - ' "\\\\'
    filter_main_cli_pipe:
        CommandLine|contains: '\\\\.\\pipe'
    condition: all of selection_* and not 1 of filter_main_*
falsepositives:
    - Unlikely
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_rundll32_unc_path/info.yml

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8124170c-5e72-4178-a4c3-a0baf42b274b

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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