A compiled Python extension is a native module that Python can import like a normal package component, but the code inside is built as a shared library instead of plain .py source. These modules are common in legitimate software because they can improve performance or wrap system-level functions in C, C++, Rust, or similar languages.
In security work, that native format matters because it changes how the file looks and behaves. A compiled extension may blend in with ordinary build artifacts, making it harder to spot during a quick review than a readable script. Attackers can abuse that trust by packaging malicious logic inside an extension delivered through a repository, installer, or code test. Defenders should treat unfamiliar native modules as high risk: inspect build instructions, verify signatures and hashes, run samples in a sandbox, and restrict execution of untrusted developer assignments.