implementing-application-whitelisting-with-applocker skill (Anthropic-Cybersecurity-Skills)

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What it does. 'Implements application whitelisting using Windows AppLocker to restrict Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).
Upstream mukul975/Anthropic-Cybersecurity-Skills
Skill file skills/implementing-application-whitelisting-with-applocker/SKILL.md
License Apache-2.0 (skill folder LICENSE)
Author mukul975
Fetched 2026-09-10

Install

  • npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill implementing-application-whitelisting-with-applocker, or copy the skill folder into ~/.claude/skills/implementing-application-whitelisting-with-applocker/.
  • Raw file: curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/implementing-application-whitelisting-with-applocker/SKILL.md

SKILL.md (verbatim)

name: implementing-application-whitelisting-with-applocker
description: 'Implements application whitelisting using Windows AppLocker to restrict
  unauthorized software execution on endpoints, reducing attack surface from malware,
  unauthorized tools, and shadow IT. Use when enforcing application control policies,
  meeting compliance requirements for software restriction, or preventing execution
  of unsigned or untrusted binaries. Activates for requests involving AppLocker, application
  whitelisting, software restriction, or executable control.

  '
domain: cybersecurity
subdomain: endpoint-security
tags:
- endpoint
- AppLocker
- application-whitelisting
- windows-security
- software-restriction
version: 1.0.0
author: mahipal
license: Apache-2.0
nist_csf:
- PR.PS-01
- PR.PS-02
- DE.CM-01
- PR.IR-01
mitre_attack:
- T1055
- T1547
- T1059
- T1036
- T1027

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:

# 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

# 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:

<!-- 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)

# 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)
  - Scripts in C:\Windows\* (default Windows scripts)
  - Approved admin scripts from \\fileserver\scripts\*

Deny (for standard users):
  - PowerShell scripts from user-writable directories
  - VBScript from %TEMP%, %APPDATA%, %USERPROFILE%\Downloads
  - JavaScript (.js) from any user-writable location

DLL Rules (optional, high performance impact):
  - Enable only in high-security environments
  - Allow signed DLLs from Program Files and Windows directories
  - Performance impact: 5-10% CPU increase during DLL loading

Step 6: Deploy in Audit Mode First

# CRITICAL: Always deploy AppLocker in Audit mode before Enforce mode
# Audit mode logs what would be blocked without actually blocking

# Set enforcement mode to Audit Only in GPO:
# AppLocker → Executable Rules → Properties → Configured: Audit only
# AppLocker → Script Rules → Properties → Configured: Audit only
# AppLocker → Windows Installer Rules → Properties → Configured: Audit only

# Ensure Application Identity service is running
Set-Service -Name AppIDSvc -StartupType Automatic
Start-Service AppIDSvc

# Link GPO to test OU
New-GPLink -Name "AppLocker-Audit-Policy" `
  -Target "OU=AppLocker-Pilot,DC=corp,DC=example,DC=com"

# Monitor audit logs for 2-4 weeks
# Event Log: Applications and Services Logs → Microsoft → Windows → AppLocker
# Event IDs:
#   8003 = EXE/DLL would be blocked
#   8006 = Script/MSI would be blocked
#   8023 = Packaged app would be blocked

Step 7: Analyze Audit Logs and Refine Rules

# Export AppLocker audit events
Get-WinEvent -LogName "Microsoft-Windows-AppLocker/EXE and DLL" `
  -FilterXPath "*[System[EventID=8003]]" |
  Select-Object TimeCreated,
    @{N='User';E={$_.Properties[0].Value}},
    @{N='FilePath';E={$_.Properties[1].Value}},
    @{N='FileHash';E={$_.Properties[4].Value}} |
  Export-Csv "C:\AppLocker\audit_blocked_exes.csv" -NoTypeInformation

# Review blocked applications
# For each blocked legitimate application:
#   1. Create a publisher rule (if signed) or path rule (if unsigned)
#   2. Add to AppLocker policy
#   3. Re-audit for 1 additional week

Step 8: Switch to Enforce Mode

# After audit period with no legitimate applications blocked:
# Change enforcement mode from Audit to Enforce

# Update GPO:
# AppLocker → Executable Rules → Properties → Configured: Enforce rules
# AppLocker → Script Rules → Properties → Configured: Enforce rules

# Phased enforcement:
# Week 1: Enforce EXE rules only
# Week 2: Enforce Script rules
# Week 3: Enforce MSI rules
# Week 4: (Optional) Enforce DLL rules

# Maintain monitoring: Event IDs 8004 (blocked EXE), 8007 (blocked script)

Key Concepts

Term Definition
Application Whitelisting Security model that allows only pre-approved applications to execute, denying everything else by default
Publisher Rule AppLocker rule based on digital signature; most resilient to application updates
Path Rule AppLocker rule based on file system path; less secure as attackers can place files in allowed paths
Hash Rule AppLocker rule based on file hash; most restrictive but breaks on every application update
LOLBin Living Off the Land Binary; legitimate OS tool abused by attackers to avoid detection
Audit Mode AppLocker logs policy violations without blocking; essential for rule refinement
Enforcement Mode AppLocker actively blocks applications that violate policy rules

Tools & Systems

  • AppLocker (built-in): Windows application control feature in Enterprise/Education editions
  • WDAC (Windows Defender Application Control): More advanced successor to AppLocker for modern Windows
  • Microsoft LAPS: Manages local admin passwords to prevent bypassing AppLocker via admin rights
  • WDAC Wizard: GUI tool for creating Windows Defender Application Control policies
  • AaronLocker: Open-source AppLocker rule generator by Microsoft employee (GitHub)

Common Pitfalls

  • Skipping Audit mode: Deploying AppLocker in Enforce mode without audit period will block critical applications and cause outages.
  • Relying solely on path rules: Users with write access to allowed paths (C:\Windows\Temp) can bypass path-based rules. Prefer publisher rules.
  • Not blocking user-writable directories: The most common gap is allowing execution from %TEMP%, Downloads, or %APPDATA%.
  • Forgetting Application Identity service: AppLocker requires the AppIDSvc service running. If it stops, all rules stop enforcing.
  • Admin bypass: Local administrators can bypass AppLocker by default. For full enforcement, combine with WDAC which enforces for all users including admins.
  • DLL rule performance: Enabling DLL rules creates significant performance overhead. Only enable in high-security environments where the tradeoff is justified.

Other files in this skill

assets/template.md (verbatim)

AppLocker Application Whitelisting Template

Policy Information

Field Value
Policy Name
Target OS Windows 10/11 Enterprise
Profile Workstation / Server / Kiosk
Enforcement Mode Audit Only / Enforce
GPO Name
Target OU
Last Updated

Approved Application Inventory

Application Publisher Version Rule Type Justification
Microsoft Office Microsoft Corporation 365 Publisher Business productivity
Google Chrome Google LLC * Publisher Approved browser
Adobe Acrobat Adobe Inc. * Publisher PDF processing

Rule Collection Configuration

Executable Rules (EXE, COM)

Rule Name Type Action Scope Conditions
Default - Windows Path Allow Everyone %WINDIR%*
Default - Program Files Path Allow Everyone %PROGRAMFILES%*
Deny - LOLBins Path Deny Standard Users mshta.exe, wscript.exe, etc.

Script Rules (PS1, BAT, CMD, VBS, JS)

Rule Name Type Action Scope Conditions
Default - Windows scripts Path Allow Everyone %WINDIR%*
Default - Program Files scripts Path Allow Everyone %PROGRAMFILES%*
Deny - User profile scripts Path Deny Standard Users %USERPROFILE%*

Windows Installer Rules (MSI, MSP, MST)

Rule Name Type Action Scope Conditions
Default - Signed MSI Publisher Allow Everyone All signed installers

LOLBin Deny List

Binary Path ATT&CK Technique Risk
mshta.exe %SYSTEM32% T1218.005 HTA execution for code delivery
wscript.exe %SYSTEM32% T1059.005 VBScript execution
cscript.exe %SYSTEM32% T1059.005 Command-line scripting
regsvr32.exe %SYSTEM32% T1218.010 COM scriptlet execution
certutil.exe %SYSTEM32% T1140 File download and decode
msbuild.exe .NET Framework T1127.001 Inline task execution

Audit Results Tracking

Audit Period Blocked Events Legitimate Blocks Rules Added Remaining Issues

Exception Register

Application Reason for Exception Compensating Control Approved By Review Date

Sign-Off

Role Name Date
Security Engineer
IT Operations Lead
Change Manager

references/api-reference.md (verbatim)

API Reference: Implementing Application Whitelisting with AppLocker

PowerShell AppLocker Management

# Export current policy
Get-AppLockerPolicy -Effective -Xml | Out-File applocker_policy.xml

# Import policy from XML
Set-AppLockerPolicy -XmlPolicy applocker_policy.xml

# Test if file is allowed
Test-AppLockerPolicy -XmlPolicy policy.xml -Path "C:\app.exe" -User Everyone

# Get AppLocker event logs
Get-WinEvent -LogName "Microsoft-Windows-AppLocker/EXE and DLL"

AppLocker Event IDs

Event ID Type Meaning
8002 EXE/DLL Allowed
8003 EXE/DLL Blocked
8004 EXE/DLL Would block (audit)
8005 Script Allowed
8006 Script Blocked
8007 Script Would block (audit)

Rule Collections

Collection File Types
Executable .exe, .com
Windows Installer .msi, .msp, .mst
Script .ps1, .bat, .cmd, .vbs, .js
DLL .dll, .ocx
Packaged App AppX/MSIX

GPO Configuration Path

Computer Configuration > Policies > Windows Settings >
  Security Settings > Application Control Policies > AppLocker

Default Rule Paths

%PROGRAMFILES%\*     - Allow Everyone
%WINDIR%\*           - Allow Everyone
*                    - Allow BUILTIN\Administrators

References

references/standards.md (verbatim)

Standards & References - Implementing Application Whitelisting with AppLocker

Primary Standards

NIST SP 800-167 - Guide to Application Whitelisting

ACSC Essential Eight - Application Control

CIS Control 2 - Software Inventory and Control

  • Publisher: Center for Internet Security
  • Relevance: CIS Controls v8 Control 2 requires software allowlisting for authorized applications

Compliance Mappings

Framework Requirement AppLocker Coverage
PCI DSS 4.0 6.4.3 - Restrict active content AppLocker script rules block unauthorized scripts
NIST 800-53 CM-7 - Least Functionality AppLocker enforces minimum required software
NIST 800-53 CM-11 - User-Installed Software AppLocker prevents unauthorized software installation
NIST 800-171 3.4.8 - Application whitelisting Direct requirement for application control
ISO 27001 A.12.5.1 - Installation of software on operational systems AppLocker restricts installation capability
HIPAA 164.312(a)(1) - Access Control Restricts executable access to authorized applications

Microsoft Documentation

Supporting References

  • LOLBAS Project: https://lolbas-project.github.io/ - Living Off The Land Binaries reference for deny rule creation
  • AaronLocker (GitHub): Open-source toolkit for generating robust AppLocker policies
  • UltimateAppLockerByPassList: Security research on AppLocker bypass techniques for defense awareness

references/workflows.md (verbatim)

Workflows - Implementing Application Whitelisting with AppLocker

Workflow 1: Initial AppLocker Deployment

[Application Inventory]
    │
    ├── Scan reference endpoints for installed applications
    ├── Catalog all approved software by publisher/path/hash
    ├── Identify admin tools vs. standard user applications
    │
    ▼
[Policy Design]
    │
    ├── Create default allow rules (Program Files, Windows)
    ├── Create publisher rules for third-party vendors
    ├── Create deny rules for LOLBins (standard users only)
    ├── Create script control rules
    │
    ▼
[Audit Mode Deployment]
    │
    ├── Deploy via GPO to pilot OU (Audit Only)
    ├── Enable Application Identity service
    ├── Monitor for 2-4 weeks
    │
    ▼
[Audit Log Analysis]
    │
    ├── Export blocked events (8003, 8006)
    ├── Identify legitimate applications being blocked
    │
    ├── Blocked app is legitimate ──► [Create allow rule]
    │                                       │
    │                                       ▼
    │                                  [Re-audit 1 week]
    │
    └── All blocked apps are unauthorized ──► [Proceed to enforcement]
                                                    │
                                                    ▼
                                               [Switch to Enforce mode (phased)]
                                                    │
                                                    ├── Week 1: EXE rules
                                                    ├── Week 2: Script rules
                                                    ├── Week 3: MSI rules
                                                    └── Week 4: DLL rules (optional)

Workflow 2: New Application Approval

[User requests new application]
    │
    ▼
[Security review of application]
    │
    ├── Is it signed by trusted publisher? ──► [Create publisher rule]
    │
    ├── Unsigned but necessary? ──► [Create hash rule + document exception]
    │
    └── Fails security review ──► [Deny request, document reason]
    │
    ▼
[Add rule to AppLocker GPO]
    │
    ▼
[Deploy to pilot OU, verify no conflicts]
    │
    ▼
[Deploy to production OU]
    │
    ▼
[Update application inventory]

Workflow 3: AppLocker Bypass Incident Response

[Detection: Unauthorized execution despite AppLocker]
    │
    ▼
[Identify bypass technique]
    │
    ├── LOLBin not blocked ──► [Add deny rule for specific binary]
    │
    ├── Execution from allowed path ──► [Restrict path rule scope]
    │
    ├── Admin user bypass ──► [Evaluate WDAC migration for admin enforcement]
    │
    └── DLL side-loading ──► [Enable DLL rules or deploy WDAC]
    │
    ▼
[Update AppLocker policy with fix]
    │
    ▼
[Verify fix in audit mode on test endpoint]
    │
    ▼
[Deploy fix to production]
    │
    ▼
[Update threat model and rule documentation]

Workflow 4: AppLocker to WDAC Migration

[Decision: Migrate from AppLocker to WDAC]
    │
    ▼
[Audit current AppLocker policy]
    │
    ├── Export AppLocker rules as XML
    ├── Identify rules that need WDAC equivalents
    │
    ▼
[Create WDAC policy using WDAC Wizard]
    │
    ├── Convert publisher rules to WDAC signer rules
    ├── Convert path rules to WDAC filepath rules
    ├── Add Microsoft recommended block rules
    │
    ▼
[Deploy WDAC in Audit mode alongside AppLocker]
    │
    ▼
[Monitor WDAC audit events for 4 weeks]
    │
    ▼
[Resolve WDAC audit findings]
    │
    ▼
[Switch WDAC to Enforce mode]
    │
    ▼
[Disable AppLocker policy]

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