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Disable or Modify Windows Defender

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Id20d52a04-b5d8-402d-88e2-7929d12cbdcd
RulenameDisable or Modify Windows Defender
DescriptionThis detection watches the commandline logs for known commands that are used to disable the Defender AV. This is based on research performed by @olafhartong on a large sample of malware for varying purposes.

Note that this detection is imperfect and is only meant to serve as basis for building a more resilient detection rule.

Make the detection more resilient, currently the order of parameters matters. You don’t want that for a production rule.

See blogpost (https://medium.com/falconforce/falconfriday-av-manipulation-0xff0e-67ed4387f9ab?source=friends_link&sk=3c7c499797bbb4d74879e102ef3ecf8f)

for more resilience considerations. The current approach can easily be bypassed by not using the powershell.exe executable.

Consider adding more ways to detect this behavior.
SeverityMedium
TacticsDefenseEvasion
TechniquesT1562.001
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/DisableOrModifyWindowsDefender.yaml
Version1.0.0
Arm template20d52a04-b5d8-402d-88e2-7929d12cbdcd.json
Deploy To Azure
let defendertampering=dynamic(["Set-MpPreference -DisableRealtimeMonitoring $true","sc stop WinDefend","sc delete WinDefend","Set-MpPreference -DisableBehaviorMonitoring $true","Set-MpPreference -ExclusionProcess", "Set-MpPreference -ExclusionExtension dll","net stop security center"]);
DeviceProcessEvents
| where ProcessCommandLine has_any (defendertampering)
// If you have a lot of false positives coming from JetBrains, you can use the line below. 
//| where InitiatingProcessFolderPath !startswith @"c:\program files\jetbrains\" and InitiatingProcessVersionInfoProductName !~ ("Android Studio")
name: Disable or Modify Windows Defender
status: Available
triggerThreshold: 0
severity: Medium
tactics:
- DefenseEvasion
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/FalconFriday/Analytic Rules/DisableOrModifyWindowsDefender.yaml
entityMappings:
- entityType: Host
  fieldMappings:
  - columnName: DeviceName
    identifier: FullName
- entityType: Account
  fieldMappings:
  - columnName: AccountSid
    identifier: Sid
  - columnName: AccountName
    identifier: Name
  - columnName: AccountDomain
    identifier: NTDomain
- entityType: Process
  fieldMappings:
  - columnName: ProcessCommandLine
    identifier: CommandLine
queryPeriod: 1h
queryFrequency: 1h
version: 1.0.0
triggerOperator: gt
description: |
  This detection watches the commandline logs for known commands that are used to disable the Defender AV. This is based on research performed by @olafhartong on a large sample of malware for varying purposes. 
  Note that this detection is imperfect and is only meant to serve as basis for building a more resilient detection rule. 
  Make the detection more resilient, currently the order of parameters matters. You don't want that for a production rule. 
  See blogpost (https://medium.com/falconforce/falconfriday-av-manipulation-0xff0e-67ed4387f9ab?source=friends_link&sk=3c7c499797bbb4d74879e102ef3ecf8f) 
  for more resilience considerations. The current approach can easily be bypassed by not using the powershell.exe executable. 
  Consider adding more ways to detect this behavior.  
query: |
  let defendertampering=dynamic(["Set-MpPreference -DisableRealtimeMonitoring $true","sc stop WinDefend","sc delete WinDefend","Set-MpPreference -DisableBehaviorMonitoring $true","Set-MpPreference -ExclusionProcess", "Set-MpPreference -ExclusionExtension dll","net stop security center"]);
  DeviceProcessEvents
  | where ProcessCommandLine has_any (defendertampering)
  // If you have a lot of false positives coming from JetBrains, you can use the line below. 
  //| where InitiatingProcessFolderPath !startswith @"c:\program files\jetbrains\" and InitiatingProcessVersionInfoProductName !~ ("Android Studio")  
relevantTechniques:
- T1562.001
id: 20d52a04-b5d8-402d-88e2-7929d12cbdcd
requiredDataConnectors:
- dataTypes:
  - DeviceProcessEvents
  connectorId: MicrosoftThreatProtection
kind: Scheduled
{
  "$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/20d52a04-b5d8-402d-88e2-7929d12cbdcd')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/20d52a04-b5d8-402d-88e2-7929d12cbdcd')]",
      "properties": {
        "alertRuleTemplateName": "20d52a04-b5d8-402d-88e2-7929d12cbdcd",
        "customDetails": null,
        "description": "This detection watches the commandline logs for known commands that are used to disable the Defender AV. This is based on research performed by @olafhartong on a large sample of malware for varying purposes. \nNote that this detection is imperfect and is only meant to serve as basis for building a more resilient detection rule. \nMake the detection more resilient, currently the order of parameters matters. You don't want that for a production rule. \nSee blogpost (https://medium.com/falconforce/falconfriday-av-manipulation-0xff0e-67ed4387f9ab?source=friends_link&sk=3c7c499797bbb4d74879e102ef3ecf8f) \nfor more resilience considerations. The current approach can easily be bypassed by not using the powershell.exe executable. \nConsider adding more ways to detect this behavior.\n",
        "displayName": "Disable or Modify Windows Defender",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "DeviceName",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "AccountSid",
                "identifier": "Sid"
              },
              {
                "columnName": "AccountName",
                "identifier": "Name"
              },
              {
                "columnName": "AccountDomain",
                "identifier": "NTDomain"
              }
            ]
          },
          {
            "entityType": "Process",
            "fieldMappings": [
              {
                "columnName": "ProcessCommandLine",
                "identifier": "CommandLine"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/FalconFriday/Analytic Rules/DisableOrModifyWindowsDefender.yaml",
        "query": "let defendertampering=dynamic([\"Set-MpPreference -DisableRealtimeMonitoring $true\",\"sc stop WinDefend\",\"sc delete WinDefend\",\"Set-MpPreference -DisableBehaviorMonitoring $true\",\"Set-MpPreference -ExclusionProcess\", \"Set-MpPreference -ExclusionExtension dll\",\"net stop security center\"]);\nDeviceProcessEvents\n| where ProcessCommandLine has_any (defendertampering)\n// If you have a lot of false positives coming from JetBrains, you can use the line below. \n//| where InitiatingProcessFolderPath !startswith @\"c:\\program files\\jetbrains\\\" and InitiatingProcessVersionInfoProductName !~ (\"Android Studio\")\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion"
        ],
        "techniques": [
          "T1562"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}