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/