What does the swift-optimizer malware do?

On `npm install`, swift-optimizer@1.1.0 runs scripts/install-binary.js as a postinstall hook. The script is a hand-rolled JavaScript bytecode VM (~123 KB) with a base64-encoded constant pool that hides all install-time behavior — platform detection, network I/O, environment reads, file writes — from source-level scanners. Decoded behavior: 1. Dropper: fetches a binary from https://telemetry021312.blob.core.windows.net/share/?v= using a spoofed Edge User-Agent, writes it to bin/swift-optimizer- (.exe), and chmods 0755. The destination is anonymous Azure blob storage; the URL is unpinned and the bytes are not hash-verified. The destination domain has no relationship to the pack

Which versions of swift-optimizer are malicious?

The following npm versions of swift-optimizer are flagged malicious: 1.1.0. Treat any of these as compromised.

How do I remediate swift-optimizer if I installed it?

Remove swift-optimizer 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.

I already installed swift-optimizer — how do I know if it already compromised me?

If swift-optimizer 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.

Is swift-optimizer part of a known attack campaign?

Yes — swift-optimizer is associated with the IN-MAL-2026-004208 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find swift-optimizer across my projects, lockfiles, and CI pipelines?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for swift-optimizer (version 1.1.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging swift-optimizer across your stack and pipelines.

Malicious package

swift-optimizernpm

Malicious code in swift-optimizer (npm) Remove it immediately and rotate any exposed credentials.

MAL-2026-4677

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

npm uninstall swift-optimizer

What this malware does

On npm install, [email protected] runs scripts/install-binary.js as a postinstall hook. The script is a hand-rolled JavaScript bytecode VM (~123 KB) with a base64-encoded constant pool that hides all install-time behavior — platform detection, network I/O, environment reads, file writes — from source-level scanners. Decoded behavior:

Dropper: fetches a binary from https://telemetry021312.blob.core.windows.net/share/?v=<checksum> using a spoofed Edge User-Agent, writes it to bin/swift-optimizer-<arch>(.exe), and chmods 0755. The destination is anonymous Azure blob storage; the URL is unpinned and the bytes are not hash-verified. The destination domain has no relationship to the package's stated author/homepage. The package's main Optimizer API is wired to invoke this binary at runtime.
Targeted-victim guardrail: getVersionChecksum reads process.env.USERDNSDOMAIN, USERDOMAIN, USERDOMAIN_ROAMINGPROFILE, os.hostname(), and an internal-IP lookup, SHA-256-hashes them, and only proceeds if the digest matches one of three hardcoded values (GUARDRAIL_DIGESTS = ['9aee64bc...','1e0ad8d7...','680326dc...']). This restricts execution to pre-identified victim organizations.
Sandbox evasion: localTestenvCheck issues an HTTPS HEAD to the RFC1918 address https://10.100.135.17/ with rejectUnauthorized:false and inspects ECONNRESET/error signals to determine whether the host is on a real corporate LAN vs. an analyst sandbox; also checks process.env.CI.
Anti-debug: process.hrtime.bigint() timing checks set a 'deception detected' flag if execution is slowed by a debugger.
Cover-story metadata: package.json author 'Bob Smith' with throwaway GitHub URL bobsmith012545/swift-optimizer and homepage releases.swift-optimizer.io — placeholder publisher consistent with a single-purpose attack package.

The combination of an unpinned anonymous-host binary drop, victim-domain hash allowlisting, RFC1918 sandbox probing, anti-debug, and bespoke bytecode-VM obfuscation has no legitimate explanation. This is a targeted supply-chain dropper.

Malicious versions

1 flagged

1.1.0

Indicators of compromise (SHA-256)

5c54f35da6df5cef65715d49fb7942aff442ee9a0cb486862031e5009277db3a

Detection & response playbook

Malicious package

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for swift-optimizer (version 1.1.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging swift-optimizer across your stack and pipelines.
If you installed it — respond
Remove swift-optimizer 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 swift-optimizer 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 swift-optimizer 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

No. swift-optimizer on npm has been identified as a malicious package (version 1.1.0 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-004208

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks swift-optimizer-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.

Malware detection Runtime egress monitoring