Base64 encoded Windows process command-lines

let ProcessCreationEvents=(union isfuzzy=true
(SecurityEvent
| where EventID==4688
| where isnotempty(CommandLine)
| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), count() by Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName,
FileName = Process, CommandLine, ParentProcessName
),
(WindowsEvent
| where EventID==4688
| where EventData has "TVqQAAMAAAAEAAA"
| extend CommandLine = tostring(EventData.CommandLine)
| where isnotempty(CommandLine)
| extend ParentProcessName = tostring(EventData.ParentProcessName)
| extend NewProcessName = tostring(EventData.NewProcessName)
| extend Process=tostring(split(NewProcessName, '\\')[-1])
| extend SubjectUserName = tostring(EventData.SubjectUserName)
| extend SubjectDomainName = tostring(EventData.SubjectDomainName)
| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), count() by Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName,
FileName = Process, CommandLine, ParentProcessName));
ProcessCreationEvents
| where CommandLine contains "TVqQAAMAAAAEAAA"
| extend HostName = iif(Computer has '.',substring(Computer,0,indexof(Computer,'.')),Computer) , DnsDomain = iif(Computer has '.',substring(Computer,indexof(Computer,'.')+1),'')

name: Base64 encoded Windows process command-lines
triggerOperator: gt
query: |
  let ProcessCreationEvents=(union isfuzzy=true
  (SecurityEvent
  | where EventID==4688
  | where isnotempty(CommandLine)
  | summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), count() by Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName,
  FileName = Process, CommandLine, ParentProcessName
  ),
  (WindowsEvent
  | where EventID==4688
  | where EventData has "TVqQAAMAAAAEAAA"
  | extend CommandLine = tostring(EventData.CommandLine)
  | where isnotempty(CommandLine)
  | extend ParentProcessName = tostring(EventData.ParentProcessName)
  | extend NewProcessName = tostring(EventData.NewProcessName)
  | extend Process=tostring(split(NewProcessName, '\\')[-1])
  | extend SubjectUserName = tostring(EventData.SubjectUserName)
  | extend SubjectDomainName = tostring(EventData.SubjectDomainName)
  | summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), count() by Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName,
  FileName = Process, CommandLine, ParentProcessName));
  ProcessCreationEvents
  | where CommandLine contains "TVqQAAMAAAAEAAA"
  | extend HostName = iif(Computer has '.',substring(Computer,0,indexof(Computer,'.')),Computer) , DnsDomain = iif(Computer has '.',substring(Computer,indexof(Computer,'.')+1),'')
queryFrequency: 1d
description: |
  'Identifies instances of a base64-encoded PE file header seen in the process command line parameter.'
id: ca67c83e-7fff-4127-a3e3-1af66d6d4cad
triggerThreshold: 0
queryPeriod: 1d
version: 1.1.5
kind: Scheduled
status: Available
severity: Medium
requiredDataConnectors:
- connectorId: SecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsSecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsForwardedEvents
  dataTypes:
  - WindowsEvent
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint%20Threat%20Protection%20Essentials/Analytic%20Rules/base64_encoded_pefile.yaml
relevantTechniques:
- T1059
- T1027
- T1140
tactics:
- Execution
- DefenseEvasion
entityMappings:
- fieldMappings:
  - identifier: Name
    columnName: Account
  entityType: Account
- fieldMappings:
  - identifier: FullName
    columnName: Computer
  - identifier: HostName
    columnName: HostName
  - identifier: DnsDomain
    columnName: DnsDomain
  entityType: Host

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/ca67c83e-7fff-4127-a3e3-1af66d6d4cad')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/ca67c83e-7fff-4127-a3e3-1af66d6d4cad')]",
      "properties": {
        "alertRuleTemplateName": "ca67c83e-7fff-4127-a3e3-1af66d6d4cad",
        "customDetails": null,
        "description": "'Identifies instances of a base64-encoded PE file header seen in the process command line parameter.'\n",
        "displayName": "Base64 encoded Windows process command-lines",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "Account",
                "identifier": "Name"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "Computer",
                "identifier": "FullName"
              },
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "DnsDomain",
                "identifier": "DnsDomain"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint%20Threat%20Protection%20Essentials/Analytic%20Rules/base64_encoded_pefile.yaml",
        "query": "let ProcessCreationEvents=(union isfuzzy=true\n(SecurityEvent\n| where EventID==4688\n| where isnotempty(CommandLine)\n| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), count() by Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName,\nFileName = Process, CommandLine, ParentProcessName\n),\n(WindowsEvent\n| where EventID==4688\n| where EventData has \"TVqQAAMAAAAEAAA\"\n| extend CommandLine = tostring(EventData.CommandLine)\n| where isnotempty(CommandLine)\n| extend ParentProcessName = tostring(EventData.ParentProcessName)\n| extend NewProcessName = tostring(EventData.NewProcessName)\n| extend Process=tostring(split(NewProcessName, '\\\\')[-1])\n| extend SubjectUserName = tostring(EventData.SubjectUserName)\n| extend SubjectDomainName = tostring(EventData.SubjectDomainName)\n| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), count() by Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName,\nFileName = Process, CommandLine, ParentProcessName));\nProcessCreationEvents\n| where CommandLine contains \"TVqQAAMAAAAEAAA\"\n| extend HostName = iif(Computer has '.',substring(Computer,0,indexof(Computer,'.')),Computer) , DnsDomain = iif(Computer has '.',substring(Computer,indexof(Computer,'.')+1),'')\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion",
          "Execution"
        ],
        "techniques": [
          "T1027",
          "T1059",
          "T1140"
        ],
        "templateVersion": "1.1.5",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}