Sigma rule: Rundll32 Execution With Uncommon DLL Extension

Rule

Title

Rundll32 Execution With Uncommon DLL Extension

Status

test

Level

medium

Author

Tim Shelton, Florian Roth (Nextron Systems), Yassine Oukessou

Date

2022-01-13

Modified

2026-10-13

File

rules/windows/process_creation/proc_creation_win_rundll32_uncommon_dll_extension.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects the execution of rundll32 with a command line that doesn't contain a common extension

Log source

product

windows

category

process_creation

Detection

selection:
    - Image|endswith: '\rundll32.exe'
    - OriginalFileName: 'RUNDLL32.EXE'
filter_main_null:
    CommandLine: null
filter_main_empty:
    CommandLine: ''
filter_main_known_extension:
    - CommandLine|contains:
          # Note: This aims to cover: single and double quotes in addition to spaces and comma "," usage.
          - '.cpl '
          - '.cpl,'
          - '.cpl"'
          - ".cpl'"
          - '.dll '
          - '.dll,'
          - '.dll"'
          - ".dll'"
          - '.inf '
          - '.inf,'
          - '.inf"'
          - ".inf'"
    - CommandLine|endswith:
          # Note: This aims to cover: single and double quotes in addition to spaces and comma "," usage.
          - '.cpl'
          - '.dll'
          - '.inf'
filter_main_localserver:
    CommandLine|contains: ' -localserver '
filter_main_zzzzInvokeManagedCustomActionOutOfProc:
    ParentImage|endswith: '\msiexec.exe'
    CommandLine|contains|all:
        - ':\Windows\Installer\'
        - '.tmp'
        - 'zzzzInvokeManagedCustomActionOutOfProc'
filter_main_streamci:
    # Windows streaming-device class installer, run by svchost (DeviceInstall) during driver setup
    # e.g. rundll32.exe streamci,StreamingDeviceSetup {eeab7790-c514-11d1-b42b-00805fc1270e},asyncmac,{...}
    Image: 'C:\Windows\System32\rundll32.exe'
    ParentImage: 'C:\Windows\System32\svchost.exe'
    CommandLine|contains: ' streamci,StreamingDeviceSetup {'
filter_optional_EdgeUpdate:
    ParentCommandLine|contains|all:
        - ':\Users\'
        - '\AppData\Local\Microsoft\EdgeUpdate\Install\{'
        - '\EDGEMITMP_'
        - '.tmp\setup.exe'
        - '--install-archive='
        - '--previous-version='
        - '--msedgewebview --verbose-logging --do-not-launch-msedge --user-level'
condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*

False positives (as the rule lists them)

• Unknown

Tags

• attack.stealth
• attack.t1218.011

MITRE ATT&CK ids this rule names

• T1218.011

References

• https://twitter.com/mrd0x/status/1481630810495139841?s=12

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_rundll32_uncommon_dll_extension.yml