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, GHSA-7vv3-8cx6-w4g3 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

swift-optimizer is a confirmed malicious npm package (MAL-2026-4677) that executes malicious code on install (malicious version 1.1.0). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in swift-optimizer (npm)

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.

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

1 flagged

1.1.0

Indicators of compromise (SHA-256)

5c54f35da6df5cef65715d49fb7942aff442ee9a0cb486862031e5009277db3a

b3b9f54ec0389f5b582a19d2d9b58c19ca92cb53792b1966da58b182d96ebf0e

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-2026-004208GHSA-7vv3-8cx6-w4g3

References

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

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