Files With System Process Name In Unsuspected Locations

title: Files With System Process Name In Unsuspected Locations
id: d5866ddf-ce8f-4aea-b28e-d96485a20d3d
status: test
description: |
    Detects the creation of an executable with a system process name in folders other than the system ones (System32, SysWOW64, etc.).
    It is highly recommended to perform an initial baseline before using this rule in production.
references:
    - Internal Research
author: Sander Wiebing, Tim Shelton, Nasreddine Bencherchali (Nextron Systems)
date: 2020-05-26
modified: 2026-07-28
tags:
    - attack.stealth
    - attack.t1036.005
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|endswith:
            - '\AtBroker.exe'
            - '\audiodg.exe'
            - '\backgroundTaskHost.exe'
            - '\bcdedit.exe'
            - '\bitsadmin.exe'
            - '\cmdl32.exe'
            - '\cmstp.exe'
            - '\conhost.exe'
            - '\csrss.exe'
            - '\dasHost.exe'
            - '\dfrgui.exe'
            - '\dllhost.exe'
            - '\dwm.exe'
            - '\eventcreate.exe'
            - '\eventvwr.exe'
            - '\explorer.exe'
            - '\extrac32.exe'
            - '\fontdrvhost.exe'
            - '\fsquirt.exe' # was seen used by sidewinder APT - https://securelist.com/sidewinder-apt/114089/
            - '\ipconfig.exe'
            - '\iscsicli.exe'
            - '\iscsicpl.exe'
            - '\logman.exe'
            - '\LogonUI.exe'
            - '\LsaIso.exe'
            - '\lsass.exe'
            - '\lsm.exe'
            - '\msiexec.exe'
            - '\msinfo32.exe'
            - '\mstsc.exe'
            - '\nbtstat.exe'
            - '\odbcconf.exe'
            - '\powershell.exe'
            - '\pwsh.exe'
            - '\regini.exe'
            - '\regsvr32.exe'
            - '\rundll32.exe'
            - '\RuntimeBroker.exe'
            - '\schtasks.exe'
            - '\SearchFilterHost.exe'
            - '\SearchIndexer.exe'
            - '\SearchProtocolHost.exe'
            - '\SecurityHealthService.exe'
            - '\SecurityHealthSystray.exe'
            - '\services.exe'
            - '\ShellAppRuntime.exe'
            - '\sihost.exe'
            - '\smartscreen.exe'
            - '\smss.exe'
            - '\spoolsv.exe'
            - '\svchost.exe'
            - '\SystemSettingsBroker.exe'
            - '\taskhost.exe'
            - '\taskhostw.exe'
            - '\Taskmgr.exe'
            - '\TiWorker.exe'
            - '\vssadmin.exe'
            - '\w32tm.exe'
            - '\WerFault.exe'
            - '\WerFaultSecure.exe'
            - '\wermgr.exe'
            - '\wevtutil.exe'
            - '\wininit.exe'
            - '\winlogon.exe'
            - '\winrshost.exe'
            - '\WinRTNetMUAHostServer.exe'
            - '\wlanext.exe'
            - '\wlrmdr.exe'
            - '\WmiPrvSE.exe'
            - '\wslhost.exe'
            - '\WSReset.exe'
            - '\WUDFHost.exe'
            - '\WWAHost.exe'
    filter_main_generic:
        # Note: It is recommended to use a more robust filter instead of this generic one, to avoid false negatives.
        TargetFilename|contains:
            # - '\SystemRoot\System32\'
            - 'C:\$WINDOWS.~BT\'
            - 'C:\$WinREAgent\'
            - 'C:\Windows\SoftwareDistribution\'
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
            - 'C:\Windows\WinSxS\'
            - 'C:\Windows\uus\'
    filter_main_tiworker:
        Image|endswith:
            - '\TiWorker.exe'
            - '\wuaucltcore.exe'
        TargetFilename|startswith: 'C:\Windows\Temp\'
    filter_main_svchost:
        Image|endswith:
            - 'C:\Windows\system32\svchost.exe'
            - 'C:\Windows\SysWOW64\svchost.exe'
        TargetFilename|contains:
            - 'C:\Program Files\WindowsApps\'
            - 'C:\Program Files (x86)\WindowsApps\'
            - '\AppData\Local\Microsoft\WindowsApps\'
    filter_main_wuauclt:
        Image:
            - 'C:\Windows\System32\wuauclt.exe'
            - 'C:\Windows\SysWOW64\wuauclt.exe'
            - 'C:\Windows\UUS\arm64\wuaucltcore.exe'
    filter_main_explorer:
        TargetFilename|endswith: 'C:\Windows\explorer.exe'
    filter_main_msiexec:
        # This filter handles system processes who are updated/installed using misexec.
        Image|endswith:
            - 'C:\WINDOWS\system32\msiexec.exe'
            - 'C:\WINDOWS\SysWOW64\msiexec.exe'
        # Add more processes if you find them or simply filter msiexec on its own. If the list grows big
        TargetFilename|startswith:
            - 'C:\Program Files\PowerShell\7\pwsh.exe'
            - 'C:\Program Files\PowerShell\7-preview\pwsh.exe'
            - 'C:\Program Files\WindowsApps\Microsoft.PowerShellPreview\'
    filter_main_healtray:
        TargetFilename|contains: 'C:\Windows\System32\SecurityHealth\'
        TargetFilename|endswith: '\SecurityHealthSystray.exe'
        Image|endswith: '\SecurityHealthSetup.exe'
    filter_optional_wslhost:
        - TargetFilename: 'C:\Program Files\WSL\wslhost.exe'
        - TargetFilename|contains|all:
              - 'C:\Program Files\WindowsApps\MicrosoftCorporationII.WindowsSubsystemForLinux_'
              - '\wslhost.exe'
        - TargetFilename|contains|all:
              - 'C:\Users\'
              - '\AppData\Local\Microsoft\WindowsApps\'
              - '\wslhost.exe'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - System processes copied outside their default folders for testing purposes
    - Third party software naming their software with the same names as the processes mentioned here
# Note: Upgrade to high after an initial baseline to your environement.
level: medium
regression_tests_path: regression_data/rules/windows/file/file_event/file_event_win_creation_system_file/info.yml