type-check-816dnpm
type-check-816d is a confirmed malicious npm package (MAL-2026-6101) that steals credentials and exfiltrates sensitive data (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in type-check-816d (npm)
What this malware does
The package declares a postinstall hook ("postinstall": "node run.js") that runs run.js automatically on npm install. run.js imports os, https, http, and child_process, reads host identifiers and environment data (process.env.USER, os.hostname(), os.platform(), process.cwd()), base64-encodes the payload (Buffer.from(...).toString('base64')), and exfiltrates it via outbound HTTP/HTTPS requests (multiple POST calls and a GET). The package name appears to be a numeric-suffixed lure with no legitimate documented purpose, and the postinstall behavior is a credential/host-recon exfiltration pattern rather than any build or setup task. Installing this package causes immediate, unattended exfiltration of installer host data to an attacker-controlled endpoint.
Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for type-check-816d (version 1.0.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging type-check-816d across your stack and pipelines.
If you installed it — respond
type-check-816d is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If type-check-816d 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 type-check-816d 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 type-check-816d-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.