The threat actor known as TeamPCP struck again, and this time they brought steganography to the party. The popular Python package telnyx was compromised in versions 4.87.1 and 4.87.2, with malware hidden inside WAV audio files to evade detection.
This is supply chain attacks 2.0, and it's getting sophisticated.
For those who don't follow security research: TeamPCP is the same group that compromised the litellm package last week. They're not script kiddies. They're organized, technically capable, and they're targeting high-value packages in the Python ecosystem with millions of downloads.
The attack chain is clever. The malicious code was injected into telnyx/_client.py, which gets executed automatically when you import the package. No user interaction needed—just pip install telnyx and you're compromised.
But here's what makes this attack notable: the payload was hidden inside WAV audio files using steganography. Network security tools scan for suspicious patterns in downloaded files, but who's checking audio files for embedded malicious code? It's a technique that bypasses a lot of standard detection mechanisms.
Once triggered, the malware behaves differently based on operating system. On Linux and macOS, it steals credentials, encrypts them with AES-256 and RSA-4096, and exfiltrates to a command-and-control server. On Windows, it drops a persistent binary in the Startup folder disguised as msbuild.exe—Microsoft's legitimate build tool.
The attention to detail is concerning. TeamPCP even pushed a quick 4.87.2 bugfix to correct a casing error in the Windows file path that was breaking persistence. These folks are monitoring their malware deployments and iterating on bugs. That's not typical for opportunistic attacks.
The broader issue is that the Python packaging ecosystem is woefully unprepared for sophisticated supply chain attacks. PyPI, the main Python package repository, has some security measures, but they're reactive rather than proactive. Package maintainers get compromised through credential theft or social engineering, and suddenly malicious code is being distributed to thousands of developers.
