Base64 encoded Windows process command-lines

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Id	ca67c83e-7fff-4127-a3e3-1af66d6d4cad
Rulename	Base64 encoded Windows process command-lines
Description	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 WindowsForwardedEvents WindowsSecurityEvents
Kind	Scheduled
Query frequency	1d
Query period	1d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint Threat Protection Essentials/Analytic Rules/base64_encoded_pefile.yaml
Version	1.1.4
Arm template	ca67c83e-7fff-4127-a3e3-1af66d6d4cad.json

KQL

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),'')

YAML

queryPeriod: 1d
requiredDataConnectors:
- connectorId: SecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsSecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsSecurityEvents
  dataTypes:
  - SecurityEvents
- connectorId: WindowsForwardedEvents
  dataTypes:
  - WindowsEvent
triggerThreshold: 0
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint Threat Protection Essentials/Analytic Rules/base64_encoded_pefile.yaml
tactics:
- Execution
- DefenseEvasion
triggerOperator: gt
severity: Medium
name: Base64 encoded Windows process command-lines
relevantTechniques:
- T1059
- T1027
- T1140
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
id: ca67c83e-7fff-4127-a3e3-1af66d6d4cad
status: Available
kind: Scheduled
entityMappings:
- fieldMappings:
  - columnName: Account
    identifier: Name
  entityType: Account
- fieldMappings:
  - columnName: Computer
    identifier: FullName
  - columnName: HostName
    identifier: HostName
  - columnName: DnsDomain
    identifier: DnsDomain
  entityType: Host
version: 1.1.4
description: |
    'Identifies instances of a base64-encoded PE file header seen in the process command line parameter.'

ARM

{
  "$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 Threat Protection Essentials/Analytic Rules/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": "1.1.4",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}