[hannob]

Well...

There's a long history of people trying to build software that detects bad software. It's known as Antivirus software. It doesn't work very well, because you're up against fundamental truths of computational theory (the halting problem).

[ComCat]

that framing is too broad for what npm supply chain attacks actually look like.

Antivirus deals with arbitrary binaries on a general purpose OS. npm attacks are much more constrained. The code has to run during install or import, steal credentials, send them over the network, and hide inside a package that claims to do something ordinary. That narrows the space.

I am not solving “is this code malicious?” in the abstract. I am checking concrete violations of behavioral invariants. A CSS library importing child_process. A utility suddenly adding obfuscated network calls in a patch release. A package reading .ssh keys during postinstall. Those patterns are not theoretical edge cases. They are how real attacks work.

No, you cannot catch everything. But every major npm supply chain incident in 2025 used the same playbook: install script abuse, credential theft, network exfiltration. That is highly detectable. The goal is not perfection. It is raising the cost of attack in a space where most attackers are currently not even trying to evade detection.