Convert indexed Sigma rules into analyst-ready detections.

title: Dbghelp/Dbgcore DLL Loaded By Uncommon/Suspicious Process
id: 0e277796-5f23-4e49-a490-483131d4f6e1
related:
    - id: bdc64095-d59a-42a2-8588-71fd9c9d9abc # Unsigned Loading
      type: similar
status: test
description: |
    Detects the load of dbghelp/dbgcore DLL by a potentially uncommon or potentially suspicious process.
    The Dbghelp and Dbgcore DLLs export functions that allow for the dump of process memory. Tools like ProcessHacker, Task Manager and some attacker tradecraft use the MiniDumpWriteDump API found in dbghelp.dll or dbgcore.dll.
    As an example, SilentTrynity C2 Framework has a module that leverages this API to dump the contents of Lsass.exe and transfer it over the network back to the attacker's machine.
    Keep in mind that many legitimate Windows processes and services might load the aforementioned DLLs for debugging or other related purposes. Investigate the CommandLine and the Image location of the process loading the DLL.
references:
    - https://docs.microsoft.com/en-us/windows/win32/api/minidumpapiset/nf-minidumpapiset-minidumpwritedump
    - https://www.pinvoke.net/default.aspx/dbghelp/MiniDumpWriteDump.html
    - https://medium.com/@fsx30/bypass-edrs-memory-protection-introduction-to-hooking-2efb21acffd6
author: Perez Diego (@darkquassar), oscd.community, Ecco
date: 2019-10-27
modified: 2024-03-01
tags:
    - attack.credential-access
    - attack.t1003.001
    - detection.threat-hunting
logsource:
    category: image_load
    product: windows
detection:
    selection:
        ImageLoaded|endswith:
            - '\dbghelp.dll'
            - '\dbgcore.dll'
        Image|endswith:
            - '\bash.exe'
            - '\cmd.exe'
            - '\cscript.exe'
            - '\dnx.exe'
            - '\excel.exe'
            - '\monitoringhost.exe'
            - '\msbuild.exe'
            - '\mshta.exe'
            - '\outlook.exe'
            - '\powerpnt.exe'
            - '\regsvcs.exe'
            - '\rundll32.exe'
            - '\sc.exe'
            - '\scriptrunner.exe'
            - '\winword.exe'
            - '\wmic.exe'
            - '\wscript.exe'
            # - '\powershell.exe' # Note: Triggered by installing common software
            # - '\regsvr32.exe'  # Note: triggered by installing common software
            # - '\schtasks.exe'  # Note: triggered by installing software
            # - '\svchost.exe'  # Note: triggered by some services
    filter_main_tiworker:
        # Note: This filter requires "CommandLine" field enrichment
        CommandLine|startswith: 'C:\WINDOWS\WinSxS\'
        CommandLine|endswith: '\TiWorker.exe -Embedding'
    filter_main_generic:
        # Note: This filter requires "CommandLine" field enrichment
        Image|endswith: '\svchost.exe'
        CommandLine|endswith:
            - '-k LocalServiceNetworkRestricted'
            - '-k WerSvcGroup'
    filter_main_rundll32:
        # Note: This filter requires "CommandLine" field enrichment
        Image|endswith: '\rundll32.exe'
        CommandLine|contains:
            - '/d srrstr.dll,ExecuteScheduledSPPCreation'
            - 'aepdu.dll,AePduRunUpdate'
            - 'shell32.dll,OpenAs_RunDL'
            - 'Windows.Storage.ApplicationData.dll,CleanupTemporaryState'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Debugging scripts might leverage this DLL in order to dump process memory for further analysis.
level: medium