A Python startup hook is code that runs automatically when the interpreter launches, potentially before an application explicitly imports a particular package. Python startup mechanisms can include site initialization and configuration that loads custom code, so execution may occur simply because an environment starts.
This matters in security investigations because malicious code can run without an obvious import in application source code. In attacks involving poisoned packages or compromised environments, startup behavior may help execute code whenever Python begins. Defenders should inspect interpreter startup configuration and environment files, review unexpected startup modules, and verify package integrity-not rely only on searching applications for direct imports.