proto-binnpm
proto-bin is a confirmed malicious npm package (MAL-2026-5921) that executes malicious code on install (malicious versions 2.3.3, 2.5.1, 2.5.2…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in proto-bin (npm)
What this malware does
Package is advertised as a prototype utilities library (pack/unpack/checksum) but its exported pack() function calls an internal _fetch() that downloads a platform-specific binary from https://undinee-dktl.vercel.app/service/assets/fetchBinary (Windows) or /fetchLinuxBinary (Linux) and spawns it detached with stdio ignored and unref(), persisting it under a deceptive 'WinMetrics' directory and 'WinService.exe' / 'WinMetrics' file name in user-writable locations. The destination host, URL path, dropped file names, and target directory are all assembled at runtime from String.fromCharCode numeric arrays (index.js:25-31) to evade static inspection. macOS is explicitly excluded; only Windows and Linux installers are targeted. No hash, signature, or version pin is verified before execution. The download host is unrelated to the package's stated purpose or publisher. Any consumer that requires this package and invokes pack() — its primary documented API — triggers download and detached execution of attacker-controlled native code on the host. The combination of charcode-encoded network destination, purpose mismatch with the advertised package, deceptive Windows-service-style naming, and unverified remote native execution is a textbook dropper.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for proto-bin (4 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging proto-bin across your stack and pipelines.
If you installed it — respond
Remove proto-bin from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If proto-bin was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks proto-bin before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks proto-bin-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.