Potential Antimalware Scan Interface Bypass via PowerShell
editPotential Antimalware Scan Interface Bypass via PowerShell
editIdentifies the execution of PowerShell script with keywords related to different Antimalware Scan Interface (AMSI) bypasses. An adversary may attempt first to disable AMSI before executing further malicious powershell scripts to evade detection.
Rule type: query
Rule indices:
- winlogbeat-*
- logs-windows.*
Severity: high
Risk score: 73
Runs every: 5m
Searches indices from: now-9m (Date Math format, see also Additional look-back time
)
Maximum alerts per execution: 100
References:
Tags:
- Elastic
- Host
- Windows
- Threat Detection
- Defense Evasion
- PowerShell
Version: 1
Rule authors:
- Elastic
Rule license: Elastic License v2
Rule query
editevent.category :"process" 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 System.Management.Automation.ScriptBlock or AmsiInitialize or unloadobfuscated or unloadsilent or AmsiX64 or AmsiX32 or FindAmsiFun) or powershell.file.script_block_text : ("[System.Runtime.InteropServices.Marshal]::Copy" and "VirtualProtect") or powershell.file.script_block_text : ("[Ref].Assembly.GetType(('System.Management.Automation" and ".SetValue(") )
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
-
Technique:
- Name: Impair Defenses
- ID: T1562
- Reference URL: https://attack.mitre.org/techniques/T1562/
-
Sub-technique:
- Name: Disable or Modify Tools
- ID: T1562.001
- Reference URL: https://attack.mitre.org/techniques/T1562/001/
-
Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
-
Technique:
- Name: Command and Scripting Interpreter
- ID: T1059
- Reference URL: https://attack.mitre.org/techniques/T1059/
-
Sub-technique:
- Name: PowerShell
- ID: T1059.001
- Reference URL: https://attack.mitre.org/techniques/T1059/001/