Malicious PowMix AMSI Bypass via amsiInitFailed

ATT&CK techniques

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects PowerShell script content that forces the amsiInitFailed condition to disable the Antimalware Scan Interface, matching the PowMix botnet loader targeting Czech users. Setting amsiInitFailed causes AMSI to skip scanning subsequent in-memory payloads, letting the fileless PowMix stager execute undetected. Presence of this bypass in script telemetry is a high-confidence evasion indicator.

Reporting behind it

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Malicious PowMix AMSI Bypass via amsiInitFailed

Pivot detection · T1685 · 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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