Elastic Defend high stable eql
Execution via Obfuscated PowerShell Script
Identifies the execution of PowerShell with potentially obfuscated content. This behavior is often observed during malware installation leveraging PowerShell.
Detection Logic
api where process.Ext.api.name == "AmsiScanBuffer" and
process.name : "powershell.exe" and user.id != "S-1-5-18" and
/* obfuscated content */
process.Ext.api.parameters.buffer : ("*-bxor*", "*:sptth*", "*//:p##h*", "*.rEplAcE(([chAr]*", "*$pShOMe[*", "*$ShellId[*", "*$env:Public[*",
"*$env:ComSpec[*", "*ecalper-*", "*]rahc[*", "*NoiSsErpXe-eKoVNi*", "*elbairav-*", "*ECNErEFERpESObREv$*", "*.Name[3,11,2]*",
"*sailA-teS*", "*]rtPtnI[*", "*-ekovnI*", "*TVqQAAMAAAAEAAAA*", "*System.Management.Automation.$([cHAr]*") and
not (process.Ext.api.parameters.buffer : "*-bxor*" and process.Ext.api.parameters.buffer : "#powershellskript *") and
not (process.Ext.api.parameters.buffer : "*-bxor*" and process.Ext.api.parameters.buffer : ("*-bxor 0xFFFF0000*", "*Ansible.Basic.AnsibleModule*")) and
not (process.Ext.api.parameters.buffer : ("function Get-DbaProductKey*", "function Invoke-DbaDbDecryptObjec*") and process.Ext.api.parameters.buffer : "* -bxor *") and
not (process.Ext.api.parameters.size >= 155000 and process.Ext.api.parameters.buffer : "*HSTITest_Encoded*TVqQAAMAAAAEAAAA*") and
not (process.Ext.api.parameters.size == 38324 and
process.command_line : "*AkAGUAeABlAGMAXwB3AHIAYQBwAHAAZQByAF8AcwB0AHIALgBTAHAAbABpAHQAKABAACgAIgBgADAAYAAwAGAAMABgADAAIgApAC*") and
not process.Ext.api.parameters.content_name :
("?:\\Program Files\\*.ps1",
"?:\\Program Files (x86)\\*.ps1",
"D:\\*", "E:\\*", "F:\\*", "I:\\*", "X:\\*",
"C:\\ProgramData\\NinjaRMMAgent\\scripting\\*.ps1",
"C:\\ProgramData\\chocolatey\\*.ps1",
"C:\\WINDOWS\\IMECache\\*",
"C:\\ProgramData\\CentraStage\\Packages\\*\\command.ps1") and
not process.command_line : "\"C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\powershell.exe\" -windowstyle hidden -nologo Invoke-Expression $env:Include" and
not process.parent.executable : ("C:\\Program Files (x86)\\ManageSoft\\Tracker\\ndtrack.exe",
"C:\\Program Files (x86)\\CentraStage\\Gui.exe",
"C:\\Program Files (x86)\\Spiceworks Agent Shell\\AgentShell.exe",
"C:\\Program Files\\SentinelOne\\Sentinel Agent *\\Addons\\SentinelAddonHost.exe",
"C:\\Program Files (x86)\\Spiceworks Agent Shell\\AgentShellService.exe",
"C:\\Program Files\\Microsoft VS Code\\Code.exe",
"C:\\Windows\\System32\\gpscript.exe",
"C:\\Program Files\\Windows Defender Advanced Threat Protection\\SenseIR.exe",
"C:\\Program Files (x86)\\Microsoft Intune Management Extension\\AgentExecutor.exe",
"C:\\Windows\\System32\\drivers\\Intel\\ICPS\\IntelConnectivityNetworkService.exe",
"C:\\Program Files\\Axis Communications\\AXIS Camera Station\\Components\\AXIS System Health Monitoring\\AXISSystemHealthMonitoring.exe") Field Validations
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