Query: hunt for Application Shimming activity
Matching passage: T1546.011 Application Shimming. Tactics: privilege escalation, persistence. Description: Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by application shims. The Microsoft Windows Application Compatibility Infrastructure/Framework (Application Shim) was created to allow for backward compatibility of software as the operating system codebase changes over time. For example, the application shimming feature allows developers to apply fixes to applications (without rewriting code) that were created for Windows XP so that it will work with Windows 10. (Citation: Elastic Process Injection July 2017) Within the framework, shims are created to act as a buffer between the program (or more specifically, the Import Address Table) and the Windows OS. When a program is executed, the shim cache is referenced to determine if the program requires the use of the shim database (.sdb). If so, the shim database uses hooking to redirect the code as necessary in order to communicate with the OS. A list of all shims currently installed by the default Windows installer (sdbinst.exe) is kept in: * <code>%WINDIR%\AppPatch\sysmain.sdb</code> and * <code>hklm\software\microsoft\windows nt\currentversion\appcompatflags\installedsdb</code> Custom databases are stored in: * <code>%WINDIR%\AppPatch\custom & %WINDIR%\AppPatch\AppPatch64\Custom</code> and * <code>hklm\software\microsoft\windows nt\currentversion\appcompatflags\custom</code> To keep shims secure, Windows designed them to run in user mode so they cannot modify the kernel and you must have administrator privileges to install a shim. However, certain shims can be used to [Bypass User Account Control](https://attack.mitre.org/techniques/T1548/002) (UAC and RedirectEXE), inject DLLs into processes (InjectDLL), disable Data Execution Prevention (DisableNX) and Structure Exception Handling (DisableSEH), and intercept memory addresses (GetProcAddress). Utilizing these shims may allow an adversary to perform several malicious acts such as elevate privileges, install backdo
Near-miss passage: T1546.018 Python Startup Hooks. Tactics: persistence, privilege escalation. Description: Adversaries may achieve persistence by leveraging Python’s startup mechanisms, including path configuration (`.pth`) files and the `sitecustomize.py` or `usercustomize.py` modules. These files are automatically processed during the initialization of the Python interpreter, allowing for the execution of arbitrary code whenever Python is invoked.(Citation: Volexity GlobalProtect CVE 2024) Path configuration files are designed to extend Python’s module search paths through the use of import statements. If a `.pth` file is placed in Python's `site-packages` or `dist-packages` directories, any lines beginning with `import` will be executed automatically on Python invocation.(Citation: DFIR Python Persistence 2025) Similarly, if `sitecustomize.py` or `usercustomize.py` is present in the Python path, these files will be imported during interpreter startup, and any code they contain will be executed.(Citation: Python Site Configuration Hook) Adversaries may abuse these mechanisms to establish persistence on systems where Python is widely used (e.g., for automation or scripting in production environments).