Suspicious npm Postinstall Node Execution From Fixtures Path (BeaverTail OtterCookie)

ATT&CK techniques

Initial Access → Execution

Recon
Resource Dev
Initial Access
- T1195.002Compromise Software Supply Chain
Execution
- T1059.007JavaScript
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects node.exe executing a script from a test fixtures eval path, the malicious npm postinstall chain used by the BeaverTail and OtterCookie malware families delivered through compromised packages. This lures developers into running staged JavaScript modules such as index.js and file15.js. Node execution from fixture directories during package installation indicates a supply-chain compromise.

Reporting behind it

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Linux File Creation Indicators for TanStack Runner and Persistence Components

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Suspicious Node Payload Drop in Local Share Directory (via file_event)

Suspicious Script Host Execution of Decoy-Named JavaScript Dropper (PS1Bot)

Malicious Emmenhtal JavaScript Loader Spawning Encoded PowerShell

Suspicious npm Postinstall Node Execution From Fixtures Path (BeaverTail OtterCookie)

Pivot detection · T1059.007 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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