Developers who mistyped the package name loaded the malicious libraries in their software's setup scripts. "These packages contain the exact same code as their upstream package thus their functionality is the same, but the installation script, setup.py, is modified to include a malicious (but relatively benign) code," NBU explained. Experts say the malicious code only collected information on infected hosts, such as name and version of the fake package, the username of the user who installed the package, and the user's computer hostname. Collected data, which looked like "Y:urllib-1.21.1 admin testmachine", was uploaded to a Chinese IP address. NBU officials contacted PyPI administrators last week who removed the packages before officials published a security advisory on Saturday."
The advisory lays some of the blame on Python's 'pip' tool, which executes arbitrary code during installations without requiring a cryptographic signature.
Ars Technica also reports that another team of researchers "was able to seed PyPI with more than 20 libraries that are part of the Python standard library," and that group now reports they've already received more than 7,400 pingbacks.