Elastic Security Detection Rules

Potential Antimalware Scan Interface Bypass via PowerShell

Last updated 8 days ago on 2026-01-26
Created 3 years ago on 2023-01-17

About

Detects PowerShell scripts that references Antimalware Scan Interface (AMSI) bypass classes, methods, or known bypass strings. Attackers attempt AMSI bypass to disable scanning and run malicious PowerShell content undetected.
Tags
Domain: EndpointOS: WindowsUse Case: Threat DetectionTactic: Defense EvasionData Source: PowerShell LogsLanguage: kuery
Severity
high
Risk Score
73
MITRE ATT&CK™

Defense Evasion (TA0005)(external, opens in a new tab or window)

↳ Impair Defenses (T1562)(external, opens in a new tab or window)

Execution (TA0002)(external, opens in a new tab or window)

↳ Command and Scripting Interpreter (T1059)(external, opens in a new tab or window)

License
Elastic License v2(external, opens in a new tab or window)

Definition

Rule Type
Query (Kibana Query Language)
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
winlogbeat-*logs-windows.powershell*
Related Integrations

windows(external, opens in a new tab or window)

Query
text code block:
event.category:"process" and host.os.type:windows and
  (
    powershell.file.script_block_text : (
      "System.Management.Automation.AmsiUtils" or
			amsiInitFailed or 
			"Invoke-AmsiBypass" or 
			"Bypass.AMSI" or 
			"amsi.dll" or 
			AntimalwareProvider  or 
			amsiSession or 
			amsiContext or
			AmsiInitialize or 
			unloadobfuscated or 
			unloadsilent or 
			AmsiX64 or 
			AmsiX32 or 
			FindAmsiFun or
		    "AllocHGlobal((9076" or
		    "[cHAr](65)+[cHaR]([byTe]0x6d)+[ChaR]([ByTe]0x73)+[CHaR]([BYte]0x69"
    ) or
    powershell.file.script_block_text:("[Ref].Assembly.GetType(('System.Management.Automation" and ".SetValue(") or
    powershell.file.script_block_text:("::AllocHGlobal((" and ".SetValue(" and "-replace" and ".NoRMALiZe(")
  ) and
  not powershell.file.script_block_text : (
    "sentinelbreakpoints" and "Set-PSBreakpoint"
  )

Install detection rules in Elastic Security

Detect Potential Antimalware Scan Interface Bypass via PowerShell in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).