NRT Base64 Encoded Windows Process Command-lines

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Id	c3e5dbaa-a540-408c-8b36-68bdfb3df088
Rulename	NRT Base64 Encoded Windows Process Command-lines
Description	This detection identifies instances of a base64 encoded PE file header seen in the process command line parameter.
Severity	Medium
Tactics	Execution DefenseEvasion
Techniques	T1059 T1027 T1140
Required data connectors	SecurityEvents WindowsSecurityEvents
Kind	NRT
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Windows Security Events/Analytic Rules/NRT_base64_encoded_pefile.yaml
Version	1.0.1
Arm template	c3e5dbaa-a540-408c-8b36-68bdfb3df088.json

KQL

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), '.'))

YAML

version: 1.0.1
name: NRT Base64 Encoded Windows Process Command-lines
severity: Medium
kind: NRT
requiredDataConnectors:
- connectorId: SecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsSecurityEvents
  dataTypes:
  - SecurityEvent
entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: SubjectUserName
    identifier: Name
  - columnName: SubjectDomainName
    identifier: NTDomain
- entityType: Host
  fieldMappings:
  - columnName: HostName
    identifier: HostName
  - columnName: DnsDomain
    identifier: DnsDomain
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), '.'))  
description: |
    'This detection identifies instances of a base64 encoded PE file header seen in the process command line parameter.'
tactics:
- Execution
- DefenseEvasion
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Windows Security Events/Analytic Rules/NRT_base64_encoded_pefile.yaml
status: Available
relevantTechniques:
- T1059
- T1027
- T1140
id: c3e5dbaa-a540-408c-8b36-68bdfb3df088

ARM

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/c3e5dbaa-a540-408c-8b36-68bdfb3df088')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/c3e5dbaa-a540-408c-8b36-68bdfb3df088')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "NRT",
      "apiVersion": "2022-11-01-preview",
      "properties": {
        "displayName": "NRT Base64 Encoded Windows Process Command-lines",
        "description": "'This detection identifies instances of a base64 encoded PE file header seen in the process command line parameter.'\n",
        "severity": "Medium",
        "enabled": true,
        "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",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Execution",
          "DefenseEvasion"
        ],
        "techniques": [
          "T1059",
          "T1027",
          "T1140"
        ],
        "alertRuleTemplateName": "c3e5dbaa-a540-408c-8b36-68bdfb3df088",
        "customDetails": null,
        "entityMappings": [
          {
            "fieldMappings": [
              {
                "columnName": "SubjectUserName",
                "identifier": "Name"
              },
              {
                "columnName": "SubjectDomainName",
                "identifier": "NTDomain"
              }
            ],
            "entityType": "Account"
          },
          {
            "fieldMappings": [
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "DnsDomain",
                "identifier": "DnsDomain"
              }
            ],
            "entityType": "Host"
          }
        ],
        "templateVersion": "1.0.1",
        "status": "Available",
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Windows Security Events/Analytic Rules/NRT_base64_encoded_pefile.yaml"
      }
    }
  ]
}