title: Potential NT API Stub Patching
id: b916cba1-b38a-42da-9223-17114d846fd6
status: experimental
description: Detects potential NT API stub patching as seen used by the project PatchingAPI
references:
    - https://github.com/D1rkMtr/UnhookingPatch
    - https://twitter.com/D1rkMtr/status/1611471891193298944?s=20
author: frack113
date: 2023/01/07
modified: 2023/01/25
tags:
    - attack.defense_evasion
    - attack.t1562.002
logsource:
    category: process_access
    product: windows
detection:
    selection:
        GrantedAccess: '0x1FFFFF'
        CallTrace|startswith: 'C:\Windows\SYSTEM32\ntdll.dll+'
        CallTrace|contains: '|UNKNOWN('
        CallTrace|endswith: ')'
    filter_generic:
        # To avoid FP with installed applications. This filter assumes that if an application is located here. The attacker has already achieved admin rights
        - SourceImage|startswith:
            - 'C:\Program Files\'
            - 'C:\Program Files (x86)\'
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
        - TargetImage|startswith:
            - 'C:\Program Files\'
            - 'C:\Program Files (x86)\'
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
    filter_thor:
        SourceImage|startswith: 'C:\Windows\Temp\asgard2-agent\'
        SourceImage|endswith: '\thor64.exe'
    filter_githubdesktop:
        SourceImage|startswith: 'C:\Users\'
        SourceImage|contains: '\AppData\Local\GitHubDesktop\app-'
        SourceImage|endswith:
            - '\GitHubDesktop.exe'
            - '\resources\app\git\usr\bin\sh.exe'
        TargetImage|startswith: 'C:\Users\'
        TargetImage|contains: '\AppData\Local\GitHubDesktop\app-'
    filter_dotnet:
        SourceImage|startswith:
            - 'C:\Windows\Microsoft.NET\Framework\v'
            - 'C:\Windows\Microsoft.NET\Framework64\v'
        SourceImage|endswith: '\NGenTask.exe'
        TargetImage|startswith:
            - 'C:\Windows\Microsoft.NET\Framework\v'
            - 'C:\Windows\Microsoft.NET\Framework64\v'
    filter_taskhost:
        SourceImage:
            - 'C:\WINDOWS\system32\taskhostw.exe'
            - 'C:\Windows\system32\taskhost.exe'
        TargetImage|startswith:
            - 'C:\Windows\Microsoft.NET\Framework\v'
            - 'C:\Windows\Microsoft.NET\Framework64\v'
        TargetImage|endswith: '\NGenTask.exe'
    filter_teams_to_update:
        SourceImage|startswith: 'C:\Users\'
        SourceImage|endswith: '\AppData\Local\Microsoft\Teams\stage\Teams.exe'
        TargetImage|startswith: 'C:\Users\'
        TargetImage|endswith: '\AppData\Local\Microsoft\Teams\Update.exe'
    filter_teams_update_regsvr32:
        SourceImage|startswith: 'C:\Users\'
        SourceImage|endswith: '\AppData\Local\Microsoft\Teams\Update.exe'
        TargetImage: 'C:\WINDOWS\SysWOW64\regsvr32.exe'
    filter_teams_update_to_teams:
        SourceImage|startswith: 'C:\Users\'
        SourceImage|endswith: '\AppData\Local\Microsoft\Teams\Update.exe'
        TargetImage|endswith: '\AppData\Local\Microsoft\Teams\stage\Teams.exe'
    condition: selection and not 1 of filter_*
falsepositives:
    - Unknown
level: medium