In-Memory AMSI Bypass via amsiInitFailed Field Manipulation in PowerShell (via ps_script)

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 a PowerShell script block that sets the amsiInitFailed field to True, the in-memory AMSI bypass used by the agent1.ps1 stage of an Azorult campaign smuggled through Google Sites. Forcing amsiInitFailed disables Antimalware Scan Interface inspection so later stages run unscanned, making this a high-confidence defense-evasion signal.

Reporting behind it

Related detections9 linkedT1685 — drag to rearrange

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In-Memory AMSI Bypass via amsiInitFailed Field Manipulation in PowerShell (via ps_script)

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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