MosaicLoader

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Id	506f4d6b-3864-4bb1-8f75-a13fb066f97a
Rulename	MosaicLoader
Description	This query looks Malware Hides Itself Among Windows Defender Exclusions to Evade Detection.
Severity	High
Tactics	DefenseEvasion
Techniques	T1562
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/Exploits/MosaicLoader.yaml
Version	1.0.0
Arm template	506f4d6b-3864-4bb1-8f75-a13fb066f97a.json

KQL

DeviceRegistryEvents 
| where ((ActionType == "RegistryValueSet") and (RegistryKey startswith @"HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows Defender\\Exclusions\\Paths" 
or RegistryKey startswith @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Exclusions\Extensions"
or RegistryKey startswith @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Exclusions\Processes"))
| extend HostName = iff(DeviceName has '.', substring(DeviceName, 0, indexof(DeviceName, '.')), DeviceName)
| extend DnsDomain = iff(DeviceName has '.', substring(DeviceName, indexof(DeviceName, '.') + 1), "")

YAML

OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Defender XDR/Analytic Rules/Exploits/MosaicLoader.yaml
tags:
- MosaicLoader
- Windows Defender Exclusions
description: |
    This query looks Malware Hides Itself Among Windows Defender Exclusions to Evade Detection.
severity: High
requiredDataConnectors:
- dataTypes:
  - DeviceRegistryEvents
  connectorId: MicrosoftThreatProtection
name: MosaicLoader
triggerThreshold: 0
tactics:
- DefenseEvasion
version: 1.0.0
relevantTechniques:
- T1562
triggerOperator: gt
entityMappings:
- entityType: Host
  fieldMappings:
  - columnName: DeviceName
    identifier: FullName
  - columnName: HostName
    identifier: HostName
  - columnName: DnsDomain
    identifier: DnsDomain
- entityType: RegistryValue
  fieldMappings:
  - columnName: RegistryValueName
    identifier: Name
  - columnName: RegistryValueData
    identifier: Value
id: 506f4d6b-3864-4bb1-8f75-a13fb066f97a
status: Available
kind: Scheduled
queryFrequency: 1h
queryPeriod: 1h
query: |
  DeviceRegistryEvents 
  | where ((ActionType == "RegistryValueSet") and (RegistryKey startswith @"HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows Defender\\Exclusions\\Paths" 
  or RegistryKey startswith @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Exclusions\Extensions"
  or RegistryKey startswith @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Exclusions\Processes"))
  | extend HostName = iff(DeviceName has '.', substring(DeviceName, 0, indexof(DeviceName, '.')), DeviceName)
  | extend DnsDomain = iff(DeviceName has '.', substring(DeviceName, indexof(DeviceName, '.') + 1), "")

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/506f4d6b-3864-4bb1-8f75-a13fb066f97a')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/506f4d6b-3864-4bb1-8f75-a13fb066f97a')]",
      "properties": {
        "alertRuleTemplateName": "506f4d6b-3864-4bb1-8f75-a13fb066f97a",
        "customDetails": null,
        "description": "This query looks Malware Hides Itself Among Windows Defender Exclusions to Evade Detection.\n",
        "displayName": "MosaicLoader",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "DeviceName",
                "identifier": "FullName"
              },
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "DnsDomain",
                "identifier": "DnsDomain"
              }
            ]
          },
          {
            "entityType": "RegistryValue",
            "fieldMappings": [
              {
                "columnName": "RegistryValueName",
                "identifier": "Name"
              },
              {
                "columnName": "RegistryValueData",
                "identifier": "Value"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Defender XDR/Analytic Rules/Exploits/MosaicLoader.yaml",
        "query": "DeviceRegistryEvents \n| where ((ActionType == \"RegistryValueSet\") and (RegistryKey startswith @\"HKEY_LOCAL_MACHINE\\\\SOFTWARE\\\\Microsoft\\\\Windows Defender\\\\Exclusions\\\\Paths\" \nor RegistryKey startswith @\"HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows Defender\\Exclusions\\Extensions\"\nor RegistryKey startswith @\"HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows Defender\\Exclusions\\Processes\"))\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",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion"
        ],
        "tags": [
          "MosaicLoader",
          "Windows Defender Exclusions"
        ],
        "techniques": [
          "T1562"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}