Malicious PowerShell AMSI Bypass via AmsiInitFailed Command Line

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 the amsiInitFailed AMSI-bypass string in a PowerShell command line, a defense-evasion technique used after Citrix Bleed exploitation to disable script scanning before running the LockBit toolkit. Setting amsiInitFailed forces AMSI to skip inspection. Detecting the string exposes an active attempt to blind endpoint script scanning.

Reporting behind it

Related detections9 linkedT1685 — drag to rearrange

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Malicious PowerShell AMSI Bypass via AmsiInitFailed Command Line

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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