Regsvr32 Rundll32 with Anomalous Parent Process

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Id	2624fc55-0998-4897-bb48-1c6422befce4
Rulename	Regsvr32 Rundll32 with Anomalous Parent Process
Description	This analytical rule looks for rundll32.exe or regsvr32.exe being spawned by abnormal processes: wscript.exe, powershell.exe, cmd.exe, pwsh.exe, cscript.exe. Blog: https://threathunt.blog/running-live-malware-for-threat-hunting-purposes/
Severity	High
Tactics	DefenseEvasion
Techniques	T1218.010 T1218.011
Required data connectors	MicrosoftThreatProtection
Kind	Scheduled
Query frequency	1h
Query period	1h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Defender XDR/Analytic Rules/Defense Evasion/Regsvr32Rundll32WithAnomalousParentProcess.yaml
Version	1.0.0
Arm template	2624fc55-0998-4897-bb48-1c6422befce4.json

KQL

DeviceProcessEvents
| where FileName has_any ("rundll32.exe","regsvr32.exe")
| where InitiatingProcessFileName has_any ("wscript.exe","powershell.exe","cmd.exe","pwsh.exe","cscript.exe")
| project TimeGenerated, DeviceName, InvestigatedProcessName=FileName, InvestigatedProcessCommandLine = ProcessCommandLine,InvestigatedProcessStartTime = ProcessCreationTime, InvestigatedProcessId = ProcessId, InitiatingProcessFileName, InitiatingProcessCommandLine, InitiatingProcessParentFileName
| join (
DeviceNetworkEvents
| where InitiatingProcessFileName has_any ("rundll32.exe","regsvr32.exe")
| where RemoteIPType == "Public"
| project DeviceName, InvestigatedProcessName=InitiatingProcessFileName, InvestigatedProcessCommandLine = InitiatingProcessCommandLine,InvestigatedProcessStartTime = InitiatingProcessCreationTime, InvestigatedProcessId = InitiatingProcessId, LocalIP, RemoteIP, RemoteUrl
) on DeviceName, InvestigatedProcessCommandLine, InvestigatedProcessId, InvestigatedProcessName, InvestigatedProcessStartTime
| project-away DeviceName1, InvestigatedProcessCommandLine1, InvestigatedProcessId1, InvestigatedProcessName1, InvestigatedProcessStartTime1
| extend HostName = iff(DeviceName has '.', substring(DeviceName, 0, indexof(DeviceName, '.')), DeviceName)
| extend DnsDomain = iff(DeviceName has '.', substring(DeviceName, indexof(DeviceName, '.') + 1), "")

YAML

queryPeriod: 1h
entityMappings:
- fieldMappings:
  - columnName: DeviceName
    identifier: FullName
  - columnName: HostName
    identifier: HostName
  - columnName: DnsDomain
    identifier: DnsDomain
  entityType: Host
- fieldMappings:
  - columnName: LocalIP
    identifier: Address
  entityType: IP
- fieldMappings:
  - columnName: RemoteIP
    identifier: Address
  entityType: IP
- fieldMappings:
  - columnName: RemoteUrl
    identifier: Url
  entityType: URL
id: 2624fc55-0998-4897-bb48-1c6422befce4
name: Regsvr32 Rundll32 with Anomalous Parent Process
status: Available
description: |
  This analytical rule looks for rundll32.exe or regsvr32.exe being spawned by abnormal processes: wscript.exe, powershell.exe, cmd.exe, pwsh.exe, cscript.exe.
  Blog: https://threathunt.blog/running-live-malware-for-threat-hunting-purposes/  
tactics:
- DefenseEvasion
triggerOperator: gt
query: |
  DeviceProcessEvents
  | where FileName has_any ("rundll32.exe","regsvr32.exe")
  | where InitiatingProcessFileName has_any ("wscript.exe","powershell.exe","cmd.exe","pwsh.exe","cscript.exe")
  | project TimeGenerated, DeviceName, InvestigatedProcessName=FileName, InvestigatedProcessCommandLine = ProcessCommandLine,InvestigatedProcessStartTime = ProcessCreationTime, InvestigatedProcessId = ProcessId, InitiatingProcessFileName, InitiatingProcessCommandLine, InitiatingProcessParentFileName
  | join (
  DeviceNetworkEvents
  | where InitiatingProcessFileName has_any ("rundll32.exe","regsvr32.exe")
  | where RemoteIPType == "Public"
  | project DeviceName, InvestigatedProcessName=InitiatingProcessFileName, InvestigatedProcessCommandLine = InitiatingProcessCommandLine,InvestigatedProcessStartTime = InitiatingProcessCreationTime, InvestigatedProcessId = InitiatingProcessId, LocalIP, RemoteIP, RemoteUrl
  ) on DeviceName, InvestigatedProcessCommandLine, InvestigatedProcessId, InvestigatedProcessName, InvestigatedProcessStartTime
  | project-away DeviceName1, InvestigatedProcessCommandLine1, InvestigatedProcessId1, InvestigatedProcessName1, InvestigatedProcessStartTime1
  | extend HostName = iff(DeviceName has '.', substring(DeviceName, 0, indexof(DeviceName, '.')), DeviceName)
  | extend DnsDomain = iff(DeviceName has '.', substring(DeviceName, indexof(DeviceName, '.') + 1), "")  
queryFrequency: 1h
triggerThreshold: 0
kind: Scheduled
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Defender XDR/Analytic Rules/Defense Evasion/Regsvr32Rundll32WithAnomalousParentProcess.yaml
requiredDataConnectors:
- dataTypes:
  - DeviceProcessEvents
  - DeviceNetworkEvents
  connectorId: MicrosoftThreatProtection
tags:
- Defense Evasion
- Image Load
- Regsvr32 Abuse
- Rundll32 Abuse
version: 1.0.0
relevantTechniques:
- T1218.010
- T1218.011
severity: High

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/2624fc55-0998-4897-bb48-1c6422befce4')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/2624fc55-0998-4897-bb48-1c6422befce4')]",
      "properties": {
        "alertRuleTemplateName": "2624fc55-0998-4897-bb48-1c6422befce4",
        "customDetails": null,
        "description": "This analytical rule looks for rundll32.exe or regsvr32.exe being spawned by abnormal processes: wscript.exe, powershell.exe, cmd.exe, pwsh.exe, cscript.exe.\nBlog: https://threathunt.blog/running-live-malware-for-threat-hunting-purposes/\n",
        "displayName": "Regsvr32 Rundll32 with Anomalous Parent Process",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "DeviceName",
                "identifier": "FullName"
              },
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "DnsDomain",
                "identifier": "DnsDomain"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "LocalIP",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "RemoteIP",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "URL",
            "fieldMappings": [
              {
                "columnName": "RemoteUrl",
                "identifier": "Url"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Defender XDR/Analytic Rules/Defense Evasion/Regsvr32Rundll32WithAnomalousParentProcess.yaml",
        "query": "DeviceProcessEvents\n| where FileName has_any (\"rundll32.exe\",\"regsvr32.exe\")\n| where InitiatingProcessFileName has_any (\"wscript.exe\",\"powershell.exe\",\"cmd.exe\",\"pwsh.exe\",\"cscript.exe\")\n| project TimeGenerated, DeviceName, InvestigatedProcessName=FileName, InvestigatedProcessCommandLine = ProcessCommandLine,InvestigatedProcessStartTime = ProcessCreationTime, InvestigatedProcessId = ProcessId, InitiatingProcessFileName, InitiatingProcessCommandLine, InitiatingProcessParentFileName\n| join (\nDeviceNetworkEvents\n| where InitiatingProcessFileName has_any (\"rundll32.exe\",\"regsvr32.exe\")\n| where RemoteIPType == \"Public\"\n| project DeviceName, InvestigatedProcessName=InitiatingProcessFileName, InvestigatedProcessCommandLine = InitiatingProcessCommandLine,InvestigatedProcessStartTime = InitiatingProcessCreationTime, InvestigatedProcessId = InitiatingProcessId, LocalIP, RemoteIP, RemoteUrl\n) on DeviceName, InvestigatedProcessCommandLine, InvestigatedProcessId, InvestigatedProcessName, InvestigatedProcessStartTime\n| project-away DeviceName1, InvestigatedProcessCommandLine1, InvestigatedProcessId1, InvestigatedProcessName1, InvestigatedProcessStartTime1\n| extend HostName = iff(DeviceName has '.', substring(DeviceName, 0, indexof(DeviceName, '.')), DeviceName)\n| extend DnsDomain = iff(DeviceName has '.', substring(DeviceName, indexof(DeviceName, '.') + 1), \"\")\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "High",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion"
        ],
        "tags": [
          "Defense Evasion",
          "Image Load",
          "Regsvr32 Abuse",
          "Rundll32 Abuse"
        ],
        "techniques": [
          "T1218"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}