Python Startup Hooks
Where this stands
One published detection covers this technique. Every one is unverified — no rule on Siemphony has been executed against real telemetry.
What the technique is
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. 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. 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. Adversaries may abuse these mechanisms to establish persistence on systems where Python is widely used (e.g., for automation or scripting in production environments).
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN0713
Defender observes unauthorized modification or creation of Python hook files such as.pth, sitecustomize.py, or usercustomize.py in Python site-packages, dist-packages, or user paths. This is often correlated with subsequent unexpected interpreter execution (e.g., python3 running without user interaction), changes in interpreter behavior (e.g., malicious imports), and outbound connections initiated from Python. Defender links write/modify actions on hook files with execve of python process and/or anomalous child process or network activity.
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