implementing-application-whitelisting-with-applocker

Files (8)

• LICENSE
• SKILL.md
• template.md · assets/
• api-reference.md · references/
• standards.md · references/
• workflows.md · references/
• agent.py · scripts/
• process.py · scripts/

SKILL.md (first lines)

# Implementing Application Whitelisting with AppLocker

## When to Use

Use this skill when:
- Implementing application control to prevent unauthorized software execution on Windows endpoints
- Meeting compliance requirements (PCI DSS 6.4.3, NIST 800-53 CM-7, ACSC Essential Eight)
- Blocking common attack vectors: living-off-the-land binaries (LOLBins), script-based attacks, unauthorized admin tools
- Restricting software installation in kiosk, POS, or high-security environments

**Do not use** this skill for macOS/Linux application control (use OS-native tools like Gatekeeper or AppArmor) or for enterprise-grade WDAC (Windows Defender Application Control) deployments.

## Prerequisites

- Windows 10/11 Enterprise or Education, or Windows Server 2016+
- Application Identity service (AppIDSvc) enabled on target endpoints
- Active Directory with Group Policy Management Console (GPMC)
- Complete application inventory of approved software
- Test OU with representative endpoints for policy validation

## Workflow

### Step 1: Inventory Approved Applications

Before creating AppLocker rules, catalog all legitimate software:

```powershell
# Generate application inventory on reference endpoint
Get-AppLockerFileInformation -Directory "C:\Program Files" -Recurse `
  -FileType Exe | Export-Csv "C:\AppLocker\app_inventory_progfiles.csv" -NoTypeInformation

Get-AppLockerFileInformation -Directory "C:\Program Files (x86)" -Recurse `
  -FileType Exe | Export-Csv "C:\AppLocker\app_inventory_progfiles86.csv" -NoTypeInformation

# Include Windows system executables
Get-AppLockerFileInformation -Directory "C:\Windows" -Recurse `
  -FileType Exe | Export-Csv "C:\AppLocker\app_inventory_windows.csv" -NoTypeInformation
```

### Step 2: Create AppLocker Policy with Default Rules

```powershell
# In Group Policy Editor (gpedit.msc) or GPMC:
# Navigate to: Computer Configuration → Policies → Windows Settings
#   → Security Settings → Application Control Policies → AppLocker

# Enable default rules for each rule collection:
# - Executable Rules: Allow Everyone to run files in Program Files and Windows
# - Windows Installer Rules: Allow Everyone to run digitally signed MSIs
# - Script Rules: Allow Everyone to run scripts in Program Files and Windows
# - Packaged App Rules: Allow Everyone to run signed packaged apps

# PowerShell: Generate default rules
$defaultRules = Get-AppLockerPolicy -Local -Xml
Set-AppLockerPolicy -XmlPolicy $defaultRules -Merge
```

### Step 3: Create Publisher-Based Rules (Preferred)

Publisher rules are the most maintainable since they survive application updates:

```xml
<!-- Example AppLocker policy XML for publisher rules -->
<RuleCollection Type="Exe" EnforcementMode="AuditOnly">
  <!-- Default: Allow Windows binaries -->
  <FilePublisherRule Id="a9e18c21-ff54-4677-b3ac-4b9a03261f6c"
    Name="Allow Microsoft signed" Description="Allow all Microsoft-signed executables"
    UserOrGroupSid="S-1-1-0" Action="Allow">
    <Conditions>
      <FilePublisherCondition PublisherName="O=MICROSOFT CORPORATION*"
        ProductName="*" BinaryName="*">
        <BinaryVersionRange LowSection="*" HighSection="*"/>
      </FilePublisherCondition>
    </Conditions>
  </FilePublisherRule>

  <!-- Allow specific third-party vendor -->
  <FilePublisherRule Id="b2e28c32-aa65-5788-c4bd-5c0b14372e7d"
    Name="Allow Adobe Acrobat" Description="Allow Adobe-signed Acrobat executables"
    UserOrGroupSid="S-1-1-0" Action="Allow">
    <Conditions>
      <FilePublisherCondition PublisherName="O=ADOBE INC.*"
        ProductName="ADOBE ACROBAT*" BinaryName="*">
        <BinaryVersionRange LowSection="*" HighSection="*"/>
      </FilePublisherCondition>
    </Conditions>
  </FilePublisherRule>
</RuleCollection>
```

### Step 4: Block Known-Abused Binaries (LOLBins)

```powershell
# Deny rules for commonly abused living-off-the-land binaries
# These are legitimate Windows tools frequently used by attackers

$denyPaths = @(
    "%SYSTEM32%\mshta.exe",
    "%SYSTEM32%\wscript.exe",
    "%SYSTEM32%\cscript.exe",
    "%SYSTEM32%\regsvr32.exe",
    "%SYSTEM32%\certutil.exe",
    "%SYSTEM32%\msbuild.exe",
    "%SYSTEM32%\installutil.exe",
    "%WINDIR%\Microsoft.NET\Framework\*\msbuild.exe",
    "%WINDIR%\Microsoft.NET\Framework64\*\msbuild.exe"
)

# Create deny rules in AppLocker policy for standard users
# Important: Deny rules take precedence over Allow rules
# Apply only to standard users (not admins who may need these tools)
```

### Step 5: Configure Script Rules

```
Script Rules (critical for preventing script-based attacks):

Allow:
  - Scripts in C:\Program Files\* (publisher or path-based)

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