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Malicious Python Package Uses Unicode to Evade Detection and Deploy Malware

A new malicious Python package called onyxproxy has been found on the Python Package Index (PyPI) repository. This package uses Unicode as a trick to evade detection and deploy an info-stealing malware. The package was uploaded to PyPI on March 15, 2023, and comes with capabilities to harvest and exfiltrate credentials and other valuable data. It has since been taken down, but not before attracting a total of 183 downloads. According to software supply chain security firm Phylum, the package incorporates its malicious behavior in a setup script that's packed with thousands of seemingly legitimate code strings. These strings include a mix of bold and italic fonts and are still readable and can be parsed by the Python interpreter, only to activate the execution of the stealer malware upon installation of the package. "An obvious and immediate benefit of this strange scheme is readability," the company noted. "Moreover, these visible differences do not prevent the code from running, which it does." This is made possible owing to the use of Unicode variants of what appears to be the same character (aka homoglyphs) to camouflage its true colors (e.g., self vs. 𝘀𝘦𝘭𝘧) among innocuous-looking functions and variables. The use of Unicode to inject vulnerabilities into source code was previously disclosed by Cambridge University researchers Nicholas Boucher and Ross Anderson in an attack technique dubbed Trojan Source. This new case of onyxproxy demonstrates that this attack technique is still being used and that Python developers need to be aware of it.


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