Convert indexed Sigma rules into analyst-ready detections.

title: Csc.EXE Execution Form Potentially Suspicious Parent
id: b730a276-6b63-41b8-bcf8-55930c8fc6ee
status: test
description: Detects a potentially suspicious parent of "csc.exe", which could be a sign of payload delivery.
references:
    - https://www.uptycs.com/blog/warzonerat-can-now-evade-with-process-hollowing
    - https://reaqta.com/2017/11/short-journey-darkvnc/
    - https://www.pwc.com/gx/en/issues/cybersecurity/cyber-threat-intelligence/yellow-liderc-ships-its-scripts-delivers-imaploader-malware.html
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), X__Junior (Nextron Systems)
date: 2019-02-11
modified: 2024-05-27
tags:
    - attack.execution
    - attack.t1059.005
    - attack.t1059.007
    - attack.defense-evasion
    - attack.t1218.005
    - attack.t1027.004
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\csc.exe'
        - OriginalFileName: 'csc.exe'
    selection_parent_generic:
        ParentImage|endswith:
            - '\cscript.exe'
            - '\excel.exe'
            - '\mshta.exe'
            - '\onenote.exe'
            - '\outlook.exe'
            - '\powerpnt.exe'
            - '\winword.exe'
            - '\wscript.exe'
    selection_parent_powershell:
        ParentImage|endswith:
            - '\powershell.exe'
            - '\pwsh.exe'
        ParentCommandLine|contains:
            - '-Encoded '
            - 'FromBase64String'
    selection_parent_susp_location:
        - ParentCommandLine|re: '([Pp]rogram[Dd]ata|%([Ll]ocal)?[Aa]pp[Dd]ata%|\\[Aa]pp[Dd]ata\\([Ll]ocal([Ll]ow)?|[Rr]oaming))\\[^\\]{1,256}$'
        - ParentCommandLine|contains:
              - ':\PerfLogs\'
              - ':\Users\Public\'
              - ':\Windows\Temp\'
              - '\Temporary Internet'
        - ParentCommandLine|contains|all:
              - ':\Users\'
              - '\Favorites\'
        - ParentCommandLine|contains|all:
              - ':\Users\'
              - '\Favourites\'
        - ParentCommandLine|contains|all:
              - ':\Users\'
              - '\Contacts\'
        - ParentCommandLine|contains|all:
              - ':\Users\'
              - '\Pictures\'
    filter_main_programfiles:
        # Note: this is a generic filter. You could baseline execution in your env for a more robust rule
        ParentImage|startswith:
            - 'C:\Program Files (x86)\' # https://twitter.com/gN3mes1s/status/1206874118282448897
            - 'C:\Program Files\' # https://twitter.com/gN3mes1s/status/1206874118282448897
    filter_main_sdiagnhost:
        ParentImage: 'C:\Windows\System32\sdiagnhost.exe' # https://twitter.com/gN3mes1s/status/1206874118282448897
    filter_main_w3p:
        ParentImage: 'C:\Windows\System32\inetsrv\w3wp.exe' # https://twitter.com/gabriele_pippi/status/1206907900268072962
    filter_optional_chocolatey:
        ParentImage: 'C:\ProgramData\chocolatey\choco.exe' # Chocolatey https://chocolatey.org/
    filter_optional_defender:
        ParentCommandLine|contains: '\ProgramData\Microsoft\Windows Defender Advanced Threat Protection'
    filter_optional_ansible:
        # Note: As ansible is widely used we exclude it with this generic filter.
        # A better option would be to filter based on script content basis or other marker while hunting
        ParentCommandLine|contains:
            # '{"failed":true,"msg":"Ansible requires PowerShell v3.0 or newer"}'
            - 'JwB7ACIAZgBhAGkAbABlAGQAIgA6AHQAcgB1AGUALAAiAG0AcwBnACIAOgAiAEEAbgBzAGkAYgBsAGUAIAByAGUAcQB1AGkAcgBlAHMAIABQAG8AdwBlAHIAUwBoAGUAbABsACAAdgAzAC4AMAAgAG8AcgAgAG4AZQB3AGUAcgAiAH0AJw'
            - 'cAewAiAGYAYQBpAGwAZQBkACIAOgB0AHIAdQBlACwAIgBtAHMAZwAiADoAIgBBAG4AcwBpAGIAbABlACAAcgBlAHEAdQBpAHIAZQBzACAAUABvAHcAZQByAFMAaABlAGwAbAAgAHYAMwAuADAAIABvAHIAIABuAGUAdwBlAHIAIgB9ACcA'
            - 'nAHsAIgBmAGEAaQBsAGUAZAAiADoAdAByAHUAZQAsACIAbQBzAGcAIgA6ACIAQQBuAHMAaQBiAGwAZQAgAHIAZQBxAHUAaQByAGUAcwAgAFAAbwB3AGUAcgBTAGgAZQBsAGwAIAB2ADMALgAwACAAbwByACAAbgBlAHcAZQByACIAfQAnA'
    condition: selection_img and 1 of selection_parent_* and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: high