Anthropic-Cybersecurity-Skills/skills/configuring-windows-defender-advanced-settings/SKILL.md

---
name: configuring-windows-defender-advanced-settings
description: >
  Configures Microsoft Defender for Endpoint (MDE) advanced protection settings including
  attack surface reduction rules, controlled folder access, network protection, and exploit
  protection. Use when hardening Windows endpoints beyond default Defender settings, deploying
  enterprise-grade endpoint protection, or meeting compliance requirements for advanced malware
  defense. Activates for requests involving Windows Defender configuration, ASR rules, MDE
  tuning, or Microsoft endpoint security.
domain: cybersecurity
subdomain: endpoint-security
tags: [endpoint, windows-security, Microsoft-Defender, ASR, exploit-protection, MDE]
version: 1.0.0
author: mahipal
license: MIT
---
# Configuring Windows Defender Advanced Settings

## When to Use

Use this skill when:
- Configuring Microsoft Defender for Endpoint (MDE) beyond default settings for enhanced protection
- Implementing Attack Surface Reduction (ASR) rules to block common attack techniques
- Enabling controlled folder access for ransomware protection
- Configuring network protection and exploit protection features
- Deploying Defender settings via Intune, SCCM, or Group Policy at enterprise scale

**Do not use** this skill for third-party EDR deployment (CrowdStrike, SentinelOne) or for Microsoft Defender for Cloud (Azure workload protection).

## Prerequisites

- Windows 10/11 Enterprise with Microsoft Defender Antivirus enabled
- Microsoft 365 E5 or Microsoft Defender for Endpoint Plan 2 license (for full MDE features)
- Microsoft Intune or SCCM for enterprise policy deployment
- Microsoft 365 Defender portal access (security.microsoft.com)
- Endpoints not running third-party AV in active mode (Defender enters passive mode)

## Workflow

### Step 1: Configure Attack Surface Reduction (ASR) Rules

ASR rules block specific behaviors commonly used by malware and attackers:

```powershell
# Enable ASR rules via PowerShell (or deploy via Intune/GPO)
# Mode: 0=Disabled, 1=Block, 2=Audit, 6=Warn

# Block executable content from email client and webmail
Set-MpPreference -AttackSurfaceReductionRules_Ids BE9BA2D9-53EA-4CDC-84E5-9B1EEEE46550 `
  -AttackSurfaceReductionRules_Actions 1

# Block all Office applications from creating child processes
Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A `
  -AttackSurfaceReductionRules_Actions 1

# Block Office applications from creating executable content
Set-MpPreference -AttackSurfaceReductionRules_Ids 3B576869-A4EC-4529-8536-B80A7769E899 `
  -AttackSurfaceReductionRules_Actions 1

# Block Office applications from injecting code into other processes
Set-MpPreference -AttackSurfaceReductionRules_Ids 75668C1F-73B5-4CF0-BB93-3ECF5CB7CC84 `
  -AttackSurfaceReductionRules_Actions 1

# Block JavaScript or VBScript from launching downloaded executable content
Set-MpPreference -AttackSurfaceReductionRules_Ids D3E037E1-3EB8-44C8-A917-57927947596D `
  -AttackSurfaceReductionRules_Actions 1

# Block execution of potentially obfuscated scripts
Set-MpPreference -AttackSurfaceReductionRules_Ids 5BEB7EFE-FD9A-4556-801D-275E5FFC04CC `
  -AttackSurfaceReductionRules_Actions 1

# Block Win32 API calls from Office macros
Set-MpPreference -AttackSurfaceReductionRules_Ids 92E97FA1-2EDF-4476-BDD6-9DD0B4DDDC7B `
  -AttackSurfaceReductionRules_Actions 1

# Block credential stealing from Windows LSASS
Set-MpPreference -AttackSurfaceReductionRules_Ids 9E6C4E1F-7D60-472F-BA1A-A39EF669E4B2 `
  -AttackSurfaceReductionRules_Actions 1

# Block process creations from PSExec and WMI commands
Set-MpPreference -AttackSurfaceReductionRules_Ids D1E49AAC-8F56-4280-B9BA-993A6D77406C `
  -AttackSurfaceReductionRules_Actions 1

# Block untrusted and unsigned processes from USB
Set-MpPreference -AttackSurfaceReductionRules_Ids B2B3F03D-6A65-4F7B-A9C7-1C7EF74A9BA4 `
  -AttackSurfaceReductionRules_Actions 1

# Block persistence through WMI event subscription
Set-MpPreference -AttackSurfaceReductionRules_Ids E6DB77E5-3DF2-4CF1-B95A-636979351E5B `
  -AttackSurfaceReductionRules_Actions 1

# Block abuse of exploited vulnerable signed drivers
Set-MpPreference -AttackSurfaceReductionRules_Ids 56A863A9-875E-4185-98A7-B882C64B5CE5 `
  -AttackSurfaceReductionRules_Actions 1
```

### Step 2: Configure Controlled Folder Access (Ransomware Protection)

```powershell
# Enable Controlled Folder Access
Set-MpPreference -EnableControlledFolderAccess Enabled

# Default protected folders: Documents, Pictures, Videos, Music, Desktop, Favorites
# Add custom protected folders
Add-MpPreference -ControlledFolderAccessProtectedFolders "C:\CriticalData"
Add-MpPreference -ControlledFolderAccessProtectedFolders "D:\SharedDrives"

# Allow specific applications to access protected folders
Add-MpPreference -ControlledFolderAccessAllowedApplications "C:\Program Files\CustomApp\app.exe"
Add-MpPreference -ControlledFolderAccessAllowedApplications "C:\Program Files\Backup\backup.exe"

# Set to Audit mode first to identify legitimate applications that need access
Set-MpPreference -EnableControlledFolderAccess AuditMode
# Event ID 1124 in Microsoft-Windows-Windows Defender/Operational log
```

### Step 3: Configure Network Protection

```powershell
# Enable Network Protection (blocks connections to malicious domains/IPs)
Set-MpPreference -EnableNetworkProtection Enabled

# Network Protection leverages Microsoft SmartScreen intelligence
# Blocks: phishing sites, exploit hosting domains, C2 domains, malware download URLs

# Set to Audit mode first:
Set-MpPreference -EnableNetworkProtection AuditMode
# Event Log: Microsoft-Windows-Windows Defender/Operational, Event ID 1125

# Configure Web Content Filtering (requires MDE P2 license)
# Managed via Microsoft 365 Defender portal:
# Settings → Endpoints → Web content filtering → Add policy
# Categories to block: Malware, Phishing, Adult content, High bandwidth
```

### Step 4: Configure Exploit Protection

```powershell
# Export current exploit protection settings
Get-ProcessMitigation -RegistryConfigFilePath "C:\Defender\current_mitigations.xml"

# Configure system-level mitigations
Set-ProcessMitigation -System -Enable DEP, SEHOP, ForceRelocateImages, BottomUp

# Configure per-application mitigations
# Example: Harden Microsoft Office against exploitation
Set-ProcessMitigation -Name "WINWORD.EXE" `
  -Enable DEP, SEHOP, ForceRelocateImages, CFG, StrictHandle

Set-ProcessMitigation -Name "EXCEL.EXE" `
  -Enable DEP, SEHOP, ForceRelocateImages, CFG, StrictHandle

Set-ProcessMitigation -Name "POWERPNT.EXE" `
  -Enable DEP, SEHOP, ForceRelocateImages, CFG, StrictHandle

# Import exploit protection configuration from XML template
Set-ProcessMitigation -PolicyFilePath "C:\Defender\exploit_protection_template.xml"
```

### Step 5: Configure Cloud-Delivered Protection

```powershell
# Enable cloud-delivered protection (real-time threat intelligence)
Set-MpPreference -MAPSReporting Advanced
Set-MpPreference -SubmitSamplesConsent SendAllSamples

# Enable Block at First Sight (BAFS)
# Requires: Cloud protection enabled + sample submission enabled
Set-MpPreference -DisableBlockAtFirstSeen $false

# Set cloud block timeout to maximum (60 seconds)
Set-MpPreference -CloudBlockLevel High
Set-MpPreference -CloudExtendedTimeout 50

# Enable potentially unwanted application (PUA) protection
Set-MpPreference -PUAProtection Enabled
```

### Step 6: Configure Scan and Update Settings

```powershell
# Configure real-time protection
Set-MpPreference -DisableRealtimeMonitoring $false
Set-MpPreference -DisableBehaviorMonitoring $false
Set-MpPreference -DisableIOAVProtection $false
Set-MpPreference -DisableScriptScanning $false

# Configure scheduled scan
Set-MpPreference -ScanScheduleQuickScanTime 12:00:00
Set-MpPreference -ScanParameters QuickScan
Set-MpPreference -ScanScheduleDay 0  # Every day
Set-MpPreference -RemediationScheduleDay 0

# Configure signature updates
Set-MpPreference -SignatureUpdateInterval 1  # Check every hour
Set-MpPreference -SignatureFallbackOrder "MicrosoftUpdateServer|MMPC"

# Enable tamper protection (prevents unauthorized changes to Defender settings)
# Managed via Microsoft 365 Defender portal:
# Settings → Endpoints → Advanced features → Tamper Protection: On
```

### Step 7: Deploy via Intune (Enterprise)

```
Intune Deployment Path:
1. Endpoint Security → Attack Surface Reduction → Create Profile
   - Platform: Windows 10 and later
   - Profile: Attack surface reduction rules
   - Configure each ASR rule to Block or Audit

2. Endpoint Security → Antivirus → Create Profile
   - Microsoft Defender Antivirus
   - Configure: Cloud protection, PUA, real-time protection

3. Endpoint Security → Antivirus → Create Profile
   - Microsoft Defender Antivirus Exclusions
   - Add path/process/extension exclusions for LOB apps

4. Devices → Configuration profiles → Create profile
   - Endpoint protection → Microsoft Defender Exploit Guard
   - Configure: Controlled Folder Access, Network Protection
```

### Step 8: Monitor in Microsoft 365 Defender Portal

```
Dashboard monitoring:
1. security.microsoft.com → Reports → Endpoints
   - Device health: Protection status across fleet
   - ASR rule detections: Which rules are triggering
   - Vulnerable devices: Missing security updates

2. Threat analytics:
   - Active threat campaigns and Defender coverage
   - Recommended security actions

3. Advanced hunting (KQL):
   DeviceEvents
   | where ActionType startswith "Asr"
   | summarize Count=count() by ActionType, FileName
   | sort by Count desc

   DeviceEvents
   | where ActionType == "ControlledFolderAccessViolationBlocked"
   | project Timestamp, DeviceName, FileName, FolderPath
```

## Key Concepts

| Term | Definition |
|------|-----------|
| **ASR Rules** | Attack Surface Reduction rules that block specific high-risk behaviors at the endpoint level |
| **Controlled Folder Access** | Ransomware protection feature that prevents unauthorized applications from modifying files in protected folders |
| **Network Protection** | Blocks outbound connections to low-reputation or known-malicious domains using SmartScreen intelligence |
| **Exploit Protection** | System and per-application memory mitigations (DEP, ASLR, CFG) to prevent exploitation |
| **BAFS (Block at First Sight)** | Cloud-based zero-day protection that holds suspicious files for cloud analysis before allowing execution |
| **Tamper Protection** | Prevents unauthorized changes to Defender security settings, even by local administrators |

## Tools & Systems

- **Microsoft 365 Defender Portal**: security.microsoft.com for centralized management and reporting
- **Microsoft Intune**: Cloud-based endpoint management for Defender policy deployment
- **PowerShell (Set-MpPreference)**: Local configuration of Defender settings
- **WDAC (Windows Defender Application Control)**: Complementary application control technology
- **Microsoft Defender for Endpoint API**: REST API for automation and custom integrations

## Common Pitfalls

- **Enabling all ASR rules in Block mode immediately**: Some ASR rules cause false positives with legitimate software (Office macros, admin scripts). Always deploy in Audit mode first and monitor for 2-4 weeks.
- **Not configuring Controlled Folder Access exclusions**: Backup software, database applications, and development tools may be blocked from writing to protected folders. Add exclusions proactively.
- **Ignoring tamper protection**: Without tamper protection, malware or insiders can disable Defender via PowerShell or registry edits. Enable tamper protection through the M365 Defender portal.
- **Running Defender alongside third-party AV**: Defender enters passive mode when third-party AV is present. Ensure you are using the intended AV solution and configure Defender appropriately (EDR-only mode if keeping third-party AV).
- **Forgetting cloud connectivity requirements**: Cloud-delivered protection and BAFS require endpoints to reach Microsoft cloud services. Verify proxy/firewall rules allow Defender cloud traffic.