Malicious AMSI Bypass via AmsiUtils amsiInitFailed Manipulation

ATT&CK techniques

Execution

Recon
Resource Dev
Initial Access
Execution
- T1059.001PowerShell
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects PowerShell script content that disables the Antimalware Scan Interface by reflecting into System.Management.Automation.AmsiUtils and setting the amsiInitFailed field to true. This in-memory AMSI bypass was observed during React2Shell CVE-2025-55182 exploitation to blind endpoint scanning before executing follow-on payloads.

Reporting behind it

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Malicious AMSI Bypass via AmsiUtils amsiInitFailed Manipulation

Pivot detection · T1059.001 · 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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