NRT Base64 Encoded Windows Process Command-lines

SecurityEvent
 | where EventID == 4688
 | where isnotempty(CommandLine)
 | where CommandLine contains "TVqQAAMAAAAEAAA"
 | extend HostName = tostring(split(Computer, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))

relevantTechniques:
- T1059
- T1027
- T1140
name: NRT Base64 Encoded Windows Process Command-lines
requiredDataConnectors:
- dataTypes:
  - SecurityEvent
  connectorId: SecurityEvents
- dataTypes:
  - SecurityEvent
  connectorId: WindowsSecurityEvents
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: SubjectAccount
  - identifier: Name
    columnName: SubjectUserName
  - identifier: NTDomain
    columnName: SubjectDomainName
  entityType: Account
- fieldMappings:
  - identifier: FullName
    columnName: Computer
  - identifier: HostName
    columnName: HostName
  - identifier: DnsDomain
    columnName: DnsDomain
  entityType: Host
query: |
  SecurityEvent
   | where EventID == 4688
   | where isnotempty(CommandLine)
   | where CommandLine contains "TVqQAAMAAAAEAAA"
   | extend HostName = tostring(split(Computer, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))  
id: c3e5dbaa-a540-408c-8b36-68bdfb3df088
tactics:
- Execution
- DefenseEvasion
version: 1.0.2
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Windows Security Events/Analytic Rules/NRT_base64_encoded_pefile.yaml
kind: NRT
severity: Medium
status: Available
description: |
    'This detection identifies instances of a base64 encoded PE file header seen in the process command line parameter.'

{
  "$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/c3e5dbaa-a540-408c-8b36-68bdfb3df088')]",
      "kind": "NRT",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/c3e5dbaa-a540-408c-8b36-68bdfb3df088')]",
      "properties": {
        "alertRuleTemplateName": "c3e5dbaa-a540-408c-8b36-68bdfb3df088",
        "customDetails": null,
        "description": "'This detection identifies instances of a base64 encoded PE file header seen in the process command line parameter.'\n",
        "displayName": "NRT Base64 Encoded Windows Process Command-lines",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "SubjectAccount",
                "identifier": "FullName"
              },
              {
                "columnName": "SubjectUserName",
                "identifier": "Name"
              },
              {
                "columnName": "SubjectDomainName",
                "identifier": "NTDomain"
              }
            ]
          },
          {
            "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/Windows Security Events/Analytic Rules/NRT_base64_encoded_pefile.yaml",
        "query": "SecurityEvent\n | where EventID == 4688\n | where isnotempty(CommandLine)\n | where CommandLine contains \"TVqQAAMAAAAEAAA\"\n | extend HostName = tostring(split(Computer, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))\n",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion",
          "Execution"
        ],
        "techniques": [
          "T1027",
          "T1059",
          "T1140"
        ],
        "templateVersion": "1.0.2"
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}