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Suspicious Windows Powershell Arguments

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Suspicious Windows Powershell Arguments

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Identifies the execution of PowerShell with suspicious argument values. This behavior is often observed during malware installation leveraging PowerShell.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-windows.*
  • logs-system.security*
  • logs-windows.sysmon_operational-*
  • logs-sentinel_one_cloud_funnel.*
  • logs-m365_defender.event-*

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: None

Tags:

  • Domain: Endpoint
  • OS: Windows
  • Use Case: Threat Detection
  • Tactic: Execution
  • Data Source: System
  • Data Source: Sysmon
  • Data Source: SentinelOne
  • Data Source: Microsoft Defender for Endpoint

Version: 201

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule query

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process where host.os.type == "windows" and event.type == "start" and
 process.name : "powershell.exe" and
  (
   process.command_line :
        (
          "*^*^*^*^*^*^*^*^*^*",
          "*`*`*`*`*",
          "*+*+*+*+*+*+*",
          "*[char[]](*)*-join*",
          "*Base64String*",
          "*[*Convert]*",
          "*.Compression.*",
          "*-join($*",
          "*.replace*",
          "*MemoryStream*",
          "*WriteAllBytes*",
          "* -enc *",
          "* -ec *",
          "* /e *",
          "* /enc *",
          "* /ec *",
          "*WebClient*",
          "*DownloadFile*",
          "*DownloadString*",
          "* iex*",
          "* iwr*",
          "*Reflection.Assembly*",
          "*Assembly.GetType*",
          "*$env:temp\\*start*",
          "*powercat*",
          "*nslookup -q=txt*",
          "*$host.UI.PromptForCredential*",
          "*Net.Sockets.TCPClient*",
          "*curl *;Start*",
          "powershell.exe \"<#*",
          "*ssh -p *",
          "*http*|iex*",
          "*@SSL\\DavWWWRoot\\*.ps1*",
          "*.lnk*.Seek(0x*",
          "*[string]::join(*",
          "*[Array]::Reverse($*",
          "* hidden $(gc *",
          "*=wscri& set*",
          "*http'+'s://*",
          "*.content|i''Ex*",
          "*//:sptth*",
          "*//:ptth*",
          "*$*=Get-Content*AppData*.SubString(*$*",
          "*=cat *AppData*.substring(*);*$*"
        ) or

      (process.args : "-c" and process.args : "&{'*") or

      (process.args : "-Outfile" and process.args : "Start*") or

      (process.args : "-bxor" and process.args : "0x*") or

      process.args : "$*$*;set-alias" or

      (process.parent.name : ("explorer.exe", "cmd.exe") and
       process.command_line : ("*-encodedCommand*", "*Invoke-webrequest*", "*WebClient*", "*Reflection.Assembly*"))
  )

Framework: MITRE ATT&CKTM

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