Regsvr32 Anomaly

SIGMA detection rule by Florian Roth (Nextron Systems), oscd.community, Tim Shelton · NOASSERTION

Detects various anomalies in relation to regsvr32.exe

title: Regsvr32 Anomaly
id: 8e2b24c9-4add-46a0-b4bb-0057b4e6187d
status: deprecated
description: Detects various anomalies in relation to regsvr32.exe
references:
    - https://subt0x10.blogspot.de/2017/04/bypass-application-whitelisting-script.html
    - https://app.any.run/tasks/34221348-072d-4b70-93f3-aa71f6ebecad/
author: Florian Roth (Nextron Systems), oscd.community, Tim Shelton
date: 2019/01/16
modified: 2023/05/26
tags:
    - attack.defense_evasion
    - attack.t1218.010
    - car.2019-04-002
    - car.2019-04-003
logsource:
    category: process_creation
    product: windows
detection:
    selection1:
        Image|endswith: '\regsvr32.exe'
        CommandLine|contains: '\Temp\'
    selection2:
        Image|endswith: '\regsvr32.exe'
        ParentImage|endswith:
            - '\powershell.exe'
            - '\pwsh.exe'
            - '\powershell_ise.exe'
    selection3:
        Image|endswith: '\regsvr32.exe'
        ParentImage|endswith: '\cmd.exe'
    selection4a:
        Image|endswith: '\regsvr32.exe'
        CommandLine|contains|all:
            - '/i:'
            - 'http'
        CommandLine|endswith: 'scrobj.dll'
    selection4b:
        Image|endswith: '\regsvr32.exe'
        CommandLine|contains|all:
            - '/i:'
            - 'ftp'
        CommandLine|endswith: 'scrobj.dll'
    selection5:
        Image|endswith: 
            - '\cscript.exe'
            - '\wscript.exe'
        ParentImage|endswith: '\regsvr32.exe'
    selection6:
        Image|endswith: '\EXCEL.EXE'
        CommandLine|contains: '..\..\..\Windows\System32\regsvr32.exe '
    selection7:
        ParentImage|endswith: '\mshta.exe'
        Image|endswith: '\regsvr32.exe'
    selection8:
        Image|endswith: '\regsvr32.exe'
        CommandLine|contains:
            - '\AppData\Local'
            - 'C:\Users\Public'
    selection9: # suspicious extensions https://twitter.com/Max_Mal_/status/1542461200797163522/photo/3
        Image|endswith: '\regsvr32.exe'
        CommandLine|endswith:
            - '.jpg'
            - '.jpeg'
            - '.png'
            - '.gif'
            - '.bin'
            - '.tmp'
            - '.temp'
            - '.txt'
    filter1:
        CommandLine|contains:
            - '\AppData\Local\Microsoft\Teams'
            - '\AppData\Local\WebEx\WebEx64\Meetings\atucfobj.dll'
    filter2:
        ParentImage: 'C:\Program Files\Box\Box\FS\streem.exe'
        CommandLine|contains: '\Program Files\Box\Box\Temp\'
    filter_legitimate:
        CommandLine|endswith: '/s C:\Windows\System32\RpcProxy\RpcProxy.dll'
    condition: 1 of selection* and not 1 of filter*
fields:
    - CommandLine
    - ParentCommandLine
falsepositives:
    - Unknown
level: high

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