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	1.1.2
Arm template	ca67c83e-7fff-4127-a3e3-1af66d6d4cad.json

KQL

let ProcessCreationEvents=() {
let processEvents=(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));
processEvents};
ProcessCreationEvents
| where CommandLine contains "TVqQAAMAAAAEAAA"
| extend timestamp = StartTimeUtc, AccountCustomEntity = Account, HostCustomEntity = Computer

YAML

tactics:
- Execution
- DefenseEvasion
severity: Medium
requiredDataConnectors:
- connectorId: SecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsSecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsSecurityEvents
  dataTypes:
  - SecurityEvents
- connectorId: WindowsForwardedEvents
  dataTypes:
  - WindowsEvent
triggerOperator: gt
query: |
  let ProcessCreationEvents=() {
  let processEvents=(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));
  processEvents};
  ProcessCreationEvents
  | where CommandLine contains "TVqQAAMAAAAEAAA"
  | extend timestamp = StartTimeUtc, AccountCustomEntity = Account, HostCustomEntity = Computer  
triggerThreshold: 0
name: Base64 encoded Windows process command-lines
kind: Scheduled
version: 1.1.2
relevantTechniques:
- T1059
- T1027
- T1140
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint Threat Protection Essentials/Analytic Rules/base64_encoded_pefile.yaml
description: |
    'Identifies instances of a base64 encoded PE file header seen in the process command line parameter.'
status: Available
queryFrequency: 1d
queryPeriod: 1d
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: AccountCustomEntity
- entityType: Host
  fieldMappings:
  - identifier: FullName
    columnName: HostCustomEntity
id: ca67c83e-7fff-4127-a3e3-1af66d6d4cad

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/ca67c83e-7fff-4127-a3e3-1af66d6d4cad')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/ca67c83e-7fff-4127-a3e3-1af66d6d4cad')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01",
      "properties": {
        "displayName": "Base64 encoded Windows process command-lines",
        "description": "'Identifies instances of a base64 encoded PE file header seen in the process command line parameter.'\n",
        "severity": "Medium",
        "enabled": true,
        "query": "let ProcessCreationEvents=() {\nlet processEvents=(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));\nprocessEvents};\nProcessCreationEvents\n| where CommandLine contains \"TVqQAAMAAAAEAAA\"\n| extend timestamp = StartTimeUtc, AccountCustomEntity = Account, HostCustomEntity = Computer\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Execution",
          "DefenseEvasion"
        ],
        "techniques": [
          "T1059",
          "T1027",
          "T1140"
        ],
        "alertRuleTemplateName": "ca67c83e-7fff-4127-a3e3-1af66d6d4cad",
        "customDetails": null,
        "entityMappings": [
          {
            "fieldMappings": [
              {
                "columnName": "AccountCustomEntity",
                "identifier": "FullName"
              }
            ],
            "entityType": "Account"
          },
          {
            "fieldMappings": [
              {
                "columnName": "HostCustomEntity",
                "identifier": "FullName"
              }
            ],
            "entityType": "Host"
          }
        ],
        "status": "Available",
        "templateVersion": "1.1.2",
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint Threat Protection Essentials/Analytic Rules/base64_encoded_pefile.yaml"
      }
    }
  ]
}