Microsoft Sentinel Analytic Rules
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Hijack Execution Flow - DLL Side-Loading

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Id3084b487-fad6-4000-9544-6085b9657290
RulenameHijack Execution Flow - DLL Side-Loading
DescriptionThis detection tries to identify all DLLs loaded by “high integrity” processes and cross-checks the DLL paths against FileCreate/FileModify events of the same DLL by a medium integrity process.

Of course, we need to do some magic to filter out false positives as much as possible. So any FileCreate/FileModify done by “NT Authoriy\System” and the “RID 500” users aren’t interesting.

Also, we only want to see the FileCreate/FileModify actions which are performed with a default or limited token elevation. If done with a full elevated token, the user is apparently admin already.
SeverityMedium
TacticsPersistence
PrivilegeEscalation
DefenseEvasion
TechniquesT1574.002
Required data connectorsMicrosoftThreatProtection
KindScheduled
Query frequency1h
Query period1h
Trigger threshold0
Trigger operatorgt
Source Urihttps://github.com/Azure/Azure-Sentinel/blob/master/Solutions/FalconFriday/Analytic Rules/DLLSideLoading.yaml
Version1.0.1
Arm template3084b487-fad6-4000-9544-6085b9657290.json
Deploy To Azure
let imls = materialize(
    DeviceImageLoadEvents
    | where InitiatingProcessIntegrityLevel in ("High", "System") and FileName !endswith ".exe"
    | project FolderPath=tolower(FolderPath), InitiatingProcessFileName, InitiatingProcessIntegrityLevel, DeviceId, DeviceName
    | distinct FolderPath, InitiatingProcessFileName, InitiatingProcessIntegrityLevel, DeviceId, DeviceName
);
imls
| join (
    DeviceFileEvents
    | where FolderPath in~ ((imls | project FolderPath)) and ActionType in ("FileCreated", "FileModified") and
    InitiatingProcessIntegrityLevel !in ("High", "System", "") and InitiatingProcessAccountSid != "S-1-5-18" and
    InitiatingProcessTokenElevation in ("TokenElevationTypeDefault", "TokenElevationTypeLimited") and InitiatingProcessAccountSid !endswith "-500"
    | extend FolderPath=tolower(FolderPath)
) on FolderPath, DeviceId, DeviceName
| project-away FolderPath1
kind: Scheduled
status: Available
triggerThreshold: 0
relevantTechniques:
- T1574.002
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/FalconFriday/Analytic Rules/DLLSideLoading.yaml
requiredDataConnectors:
- dataTypes:
  - DeviceFileEvents
  - DeviceImageLoadEvents
  connectorId: MicrosoftThreatProtection
queryPeriod: 1h
tactics:
- Persistence
- PrivilegeEscalation
- DefenseEvasion
severity: Medium
triggerOperator: gt
description: |
  This detection tries to identify all DLLs loaded by "high integrity" processes and cross-checks the DLL paths against FileCreate/FileModify events of the same DLL by a medium integrity process.
  Of course, we need to do some magic to filter out false positives as much as possible. So any FileCreate/FileModify done by "NT Authoriy\System" and the "RID 500" users aren't interesting.
  Also, we only want to see the FileCreate/FileModify actions which are performed with a default or limited token elevation. If done with a full elevated token, the user is apparently admin already.  
query: |
  let imls = materialize(
      DeviceImageLoadEvents
      | where InitiatingProcessIntegrityLevel in ("High", "System") and FileName !endswith ".exe"
      | project FolderPath=tolower(FolderPath), InitiatingProcessFileName, InitiatingProcessIntegrityLevel, DeviceId, DeviceName
      | distinct FolderPath, InitiatingProcessFileName, InitiatingProcessIntegrityLevel, DeviceId, DeviceName
  );
  imls
  | join (
      DeviceFileEvents
      | where FolderPath in~ ((imls | project FolderPath)) and ActionType in ("FileCreated", "FileModified") and
      InitiatingProcessIntegrityLevel !in ("High", "System", "") and InitiatingProcessAccountSid != "S-1-5-18" and
      InitiatingProcessTokenElevation in ("TokenElevationTypeDefault", "TokenElevationTypeLimited") and InitiatingProcessAccountSid !endswith "-500"
      | extend FolderPath=tolower(FolderPath)
  ) on FolderPath, DeviceId, DeviceName
  | project-away FolderPath1  
name: Hijack Execution Flow - DLL Side-Loading
version: 1.0.1
id: 3084b487-fad6-4000-9544-6085b9657290
queryFrequency: 1h
entityMappings:
- entityType: Host
  fieldMappings:
  - columnName: DeviceName
    identifier: FullName
- entityType: Account
  fieldMappings:
  - columnName: InitiatingProcessAccountSid
    identifier: Sid
  - columnName: InitiatingProcessAccountName
    identifier: Name
  - columnName: InitiatingProcessAccountDomain
    identifier: NTDomain
- entityType: Process
  fieldMappings:
  - columnName: InitiatingProcessCommandLine
    identifier: CommandLine
{
  "$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/3084b487-fad6-4000-9544-6085b9657290')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/3084b487-fad6-4000-9544-6085b9657290')]",
      "properties": {
        "alertRuleTemplateName": "3084b487-fad6-4000-9544-6085b9657290",
        "customDetails": null,
        "description": "This detection tries to identify all DLLs loaded by \"high integrity\" processes and cross-checks the DLL paths against FileCreate/FileModify events of the same DLL by a medium integrity process.\nOf course, we need to do some magic to filter out false positives as much as possible. So any FileCreate/FileModify done by \"NT Authoriy\\System\" and the \"RID 500\" users aren't interesting.\nAlso, we only want to see the FileCreate/FileModify actions which are performed with a default or limited token elevation. If done with a full elevated token, the user is apparently admin already.\n",
        "displayName": "Hijack Execution Flow - DLL Side-Loading",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "DeviceName",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "InitiatingProcessAccountSid",
                "identifier": "Sid"
              },
              {
                "columnName": "InitiatingProcessAccountName",
                "identifier": "Name"
              },
              {
                "columnName": "InitiatingProcessAccountDomain",
                "identifier": "NTDomain"
              }
            ]
          },
          {
            "entityType": "Process",
            "fieldMappings": [
              {
                "columnName": "InitiatingProcessCommandLine",
                "identifier": "CommandLine"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/FalconFriday/Analytic Rules/DLLSideLoading.yaml",
        "query": "let imls = materialize(\n    DeviceImageLoadEvents\n    | where InitiatingProcessIntegrityLevel in (\"High\", \"System\") and FileName !endswith \".exe\"\n    | project FolderPath=tolower(FolderPath), InitiatingProcessFileName, InitiatingProcessIntegrityLevel, DeviceId, DeviceName\n    | distinct FolderPath, InitiatingProcessFileName, InitiatingProcessIntegrityLevel, DeviceId, DeviceName\n);\nimls\n| join (\n    DeviceFileEvents\n    | where FolderPath in~ ((imls | project FolderPath)) and ActionType in (\"FileCreated\", \"FileModified\") and\n    InitiatingProcessIntegrityLevel !in (\"High\", \"System\", \"\") and InitiatingProcessAccountSid != \"S-1-5-18\" and\n    InitiatingProcessTokenElevation in (\"TokenElevationTypeDefault\", \"TokenElevationTypeLimited\") and InitiatingProcessAccountSid !endswith \"-500\"\n    | extend FolderPath=tolower(FolderPath)\n) on FolderPath, DeviceId, DeviceName\n| project-away FolderPath1\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion",
          "Persistence",
          "PrivilegeEscalation"
        ],
        "techniques": [
          "T1574"
        ],
        "templateVersion": "1.0.1",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}