Researchers have discovered a novel attack on the Python Package deal Index (PyPI) repository that employs compiled Python code to sidestep detection by software security instruments.
“It may possibly be the initially provide chain attack to get advantage of the actuality that Python bytecode (PYC) documents can be straight executed,” ReversingLabs analyst Karlo Zanki reported in a report shared with The Hacker Information.
The package deal in query is fshec2, which was taken out from the deal registry on April 17, 2023, following dependable disclosure on the very same working day.
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PYC data files are compiled bytecode documents that are created by the Python interpreter when a Python application is executed.
“When a module is imported for the initially time (or when the source file has changed because the present compiled file was designed) a .pyc file that contains the compiled code must be designed in a __pycache__ subdirectory of the directory made up of the .py file,” describes the Python documentation.
The deal, for every the software supply chain security firm, contains 3 files – _init_.py, principal.py, and comprehensive.pyc – the past of which harbors destructive features.
“The entry stage of the offer was located in the __init__.py file, which imports a perform from the other plaintext file, most important.py, which consists of Python resource code liable for loading of the Python compiled module situated in one particular of the other documents, complete.pyc,” Zanki pointed out.
This, in switch, is obtained by creating use of the importlib bundle (as opposed to a frequent import) to load and execute the code existing in the .pyc file.
An assessment of the reverse-engineered edition of the PYC file reveals that it is really configured to collect usernames, hostnames, and directory listings, as perfectly as fetch commands to be executed on the host from a hard-coded server (13.51.44[.]246).
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ReversingLabs mentioned it also noticed the module download and operate one more Python script which is accountable for fetching new commands put inside of a file that can be tweaked at will by the danger actor to issue various recommendations.
Further more evaluation of the command-and-control server unearthed a misconfiguration that manufactured it doable to download data files by their ID, which are numbered in sequential buy (starting from 1), sans any authorization. This suggests that the attack was most very likely not orchestrated by a sophisticated actor.
The development is a continuation of attempts on the portion of danger actors to undertake unique obfuscation techniques in buy to evade detection from security answers.
“Loader scripts these as these learned in the fshec2 offer have a minimal amount of money of Python code and conduct a basic motion: loading of a compiled Python module,” Zanki reported. “It just comes about to be a malicious module.”
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Some pieces of this report are sourced from:
thehackernews.com