Base64 encoded Windows process command-lines Normalized Process Events

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Id	f8b3c49c-4087-499b-920f-0dcfaff0cbca
Rulename	Base64 encoded Windows process command-lines (Normalized Process Events)
Description	Identifies instances of a base64 encoded PE file header seen in the process command line parameter. To use this analytics rule, make sure you have deployed the ASIM normalization parsers
Severity	Medium
Tactics	Execution DefenseEvasion
Techniques	T1059 T1027 T1140
Kind	Scheduled
Query frequency	1d
Query period	1d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimProcess/imProcess_base64_encoded_pefile.yaml
Version	1.1.4
Arm template	f8b3c49c-4087-499b-920f-0dcfaff0cbca.json

KQL

imProcessCreate
| where CommandLine contains "TVqQAAMAAAAEAAA"
| where isnotempty(Process)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), count() by Dvc, ActorUsername, Process, CommandLine, ActingProcessName, EventVendor, EventProduct
| extend AccountName = tostring(split(ActorUsername, @'\')[1]), AccountNTDomain = tostring(split(ActorUsername, @'\')[0])
| extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)
| project-away DomainIndex

YAML

triggerOperator: gt
queryFrequency: 1d
description: |
  'Identifies instances of a base64 encoded PE file header seen in the process command line parameter.
  To use this analytics rule, make sure you have deployed the [ASIM normalization parsers](https://aka.ms/ASimProcessEvent)'  
version: 1.1.4
kind: Scheduled
triggerThreshold: 0
requiredDataConnectors: []
queryPeriod: 1d
name: Base64 encoded Windows process command-lines (Normalized Process Events)
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimProcess/imProcess_base64_encoded_pefile.yaml
id: f8b3c49c-4087-499b-920f-0dcfaff0cbca
tags:
- version: 1.0.0
  Id: ca67c83e-7fff-4127-a3e3-1af66d6d4cad
- Schema: ASIMProcessEvent
  SchemaVersion: 0.1.0
tactics:
- Execution
- DefenseEvasion
metadata:
  source:
    kind: Community
  author:
    name: Yuval Naor
  categories:
    domains:
    - Security - Threat Protection
  support:
    tier: Community
relevantTechniques:
- T1059
- T1027
- T1140
severity: Medium
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: ActorUsername
  - identifier: Name
    columnName: AccountName
  - identifier: NTDomain
    columnName: AccountNTDomain
  entityType: Account
- fieldMappings:
  - identifier: FullName
    columnName: Dvc
  - identifier: HostName
    columnName: HostName
  - identifier: DnsDomain
    columnName: HostNameDomain
  entityType: Host
query: |
  imProcessCreate
  | where CommandLine contains "TVqQAAMAAAAEAAA"
  | where isnotempty(Process)
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), count() by Dvc, ActorUsername, Process, CommandLine, ActingProcessName, EventVendor, EventProduct
  | extend AccountName = tostring(split(ActorUsername, @'\')[1]), AccountNTDomain = tostring(split(ActorUsername, @'\')[0])
  | extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)
  | project-away DomainIndex

ARM

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2023-02-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/f8b3c49c-4087-499b-920f-0dcfaff0cbca')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/f8b3c49c-4087-499b-920f-0dcfaff0cbca')]",
      "properties": {
        "alertRuleTemplateName": "f8b3c49c-4087-499b-920f-0dcfaff0cbca",
        "customDetails": null,
        "description": "'Identifies instances of a base64 encoded PE file header seen in the process command line parameter.\nTo use this analytics rule, make sure you have deployed the [ASIM normalization parsers](https://aka.ms/ASimProcessEvent)'\n",
        "displayName": "Base64 encoded Windows process command-lines (Normalized Process Events)",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "ActorUsername",
                "identifier": "FullName"
              },
              {
                "columnName": "AccountName",
                "identifier": "Name"
              },
              {
                "columnName": "AccountNTDomain",
                "identifier": "NTDomain"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "Dvc",
                "identifier": "FullName"
              },
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "HostNameDomain",
                "identifier": "DnsDomain"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimProcess/imProcess_base64_encoded_pefile.yaml",
        "query": "imProcessCreate\n| where CommandLine contains \"TVqQAAMAAAAEAAA\"\n| where isnotempty(Process)\n| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), count() by Dvc, ActorUsername, Process, CommandLine, ActingProcessName, EventVendor, EventProduct\n| extend AccountName = tostring(split(ActorUsername, @'\\')[1]), AccountNTDomain = tostring(split(ActorUsername, @'\\')[0])\n| extend HostName = tostring(split(Dvc, \".\")[0]), DomainIndex = toint(indexof(Dvc, '.'))\n| extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)\n| project-away DomainIndex\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "severity": "Medium",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion",
          "Execution"
        ],
        "tags": [
          {
            "Id": "ca67c83e-7fff-4127-a3e3-1af66d6d4cad",
            "version": "1.0.0"
          },
          {
            "Schema": "ASIMProcessEvent",
            "SchemaVersion": "0.1.0"
          }
        ],
        "techniques": [
          "T1027",
          "T1059",
          "T1140"
        ],
        "templateVersion": "1.1.4",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}