The arrival of an open-source AppLocker policy generator aimed at simplifying XML policy creation for Windows administrators deserves attention: AppLockerGen promises a lightweight, web-like interface to author, merge, inspect, and export AppLocker policies — but the tool’s appeal comes with real operational caveats that every enterprise IT team should weigh before adopting it.
AppLocker is Microsoft’s built-in application control framework that lets administrators define which executables, scripts, installers, DLLs, and packaged apps may run on Windows devices. It supports rule conditions by path, publisher (code signing), and file hash, and AppLocker policies are typically authored and deployed via Group Policy or an MDM channel. AppLocker includes default rule collections and supports both Audit only and Enforce rules modes to ease staged rollouts and testing. For administrators, AppLocker offers a powerful, native path to application allowlisting — when designed and tested carefully. (learn.microsoft.com)
AppLockerGen (often shown as AppLockerGen or ApplockerGEN in its repository) is an open-source project hosted on GitHub that presents a Streamlit-based UI for building and editing AppLocker XML policy files. The project’s README and repository show a small Python/Streamlit application designed to import/export AppLocker XML, create rules across EXE, DLL, Script, MSI, and Appx collections, merge multiple policy files, and provide helpers such as pre-built policy templates and an “inspector” for auditing rules. The project is distributed under an Apache-2.0 license on GitHub and advertises a live Streamlit demo at applockergen.streamlit.app (the repo is the authoritative source for the code and license). (github.com)
There’s also a broader context: AppLocker is part of a layered application-control strategy. Organizations often combine AppLocker with Windows Defender Application Control (WDAC), Endpoint Detection and Response (EDR), and other device-control measures to achieve robust protection. Tools that make policy generation easier should be considered in a broader defenses-in-depth plan rather than as a single silver-bullet control. The ecosystem of community tooling and docs also contains cautionary accounts of AppLocker rules unexpectedly blocking valid software; that real-world context should inform any adoption plan. (learn.microsoft.com)
AppLocker remains effective when correctly applied, but it has well-documented failure modes, deployment nuances, and bypass techniques that require attention from security practitioners. Use AppLockerGen as a drafting and validation aid — not as an automated deployment shortcut — and always follow Microsoft’s recommended testing flows (reference devices, Test-AppLockerPolicy, audit staging) before flipping enforcement to Enforce. Keep policy XML versioned, review templates and inspector outputs, and pair AppLocker with WDAC/EDR and logging to close practical gaps. (learn.microsoft.com, en.wikipedia.org)
Source: BornCity Open Source AppLocker Policy Generator | Born's Tech and Windows World
Background
AppLocker is Microsoft’s built-in application control framework that lets administrators define which executables, scripts, installers, DLLs, and packaged apps may run on Windows devices. It supports rule conditions by path, publisher (code signing), and file hash, and AppLocker policies are typically authored and deployed via Group Policy or an MDM channel. AppLocker includes default rule collections and supports both Audit only and Enforce rules modes to ease staged rollouts and testing. For administrators, AppLocker offers a powerful, native path to application allowlisting — when designed and tested carefully. (learn.microsoft.com)AppLockerGen (often shown as AppLockerGen or ApplockerGEN in its repository) is an open-source project hosted on GitHub that presents a Streamlit-based UI for building and editing AppLocker XML policy files. The project’s README and repository show a small Python/Streamlit application designed to import/export AppLocker XML, create rules across EXE, DLL, Script, MSI, and Appx collections, merge multiple policy files, and provide helpers such as pre-built policy templates and an “inspector” for auditing rules. The project is distributed under an Apache-2.0 license on GitHub and advertises a live Streamlit demo at applockergen.streamlit.app (the repo is the authoritative source for the code and license). (github.com)
What AppLockerGen claims to do
AppLockerGen’s public materials and repository describe several core capabilities aimed at reducing friction around AppLocker policy creation and management:- Policy creation and editing: A GUI to create allow/deny rules for Exe, Script, Msi, Dll, and Appx rule collections; choose rule conditions (path/publisher/hash) and enforcement modes (Audit/Enforce). (github.com)
- Import / Export: Upload existing AppLocker XML policies for modification, and export policies ready for deployment (GPO or MDM). (github.com)
- Merge policies: Combine multiple AppLocker XML files into a single consolidated policy file to simplify layered rule sets or to reconcile policy fragments from different teams. (github.com)
- Pre-built policies and templates: Downloadable starting policies that claim to block common or known-risky applications, intended as time-savers or examples. (github.com)
- Inspector / Audit helpers: Tools to validate policy formatting and surface misconfigurations before deployment; visual feedback intended to prevent malformed XML from reaching endpoints. (github.com)
- Atomic testing / Bypass list: A curated reference list of known AppLocker bypass techniques and atomic testing checks to help defenders understand edge cases and common attack patterns. (The presence and comprehensiveness of such a list in the project should be verified by reviewing the repository or demo before relying on it.) (github.com)
Why this matters for enterprise administrators
AppLocker is powerful but unforgiving when misconfigured. Many organizations have learned the hard way that importing a policy or flipping enforcement from Audit to Enforce without careful testing can produce widespread application outages, because overly broad deny rules or incorrectly authored publisher/path conditions can block critical system components. Microsoft’s guidance stresses using reference devices, the automatically generate rules wizard, and PowerShell cmdlets (e.g., New-AppLockerPolicy, Test-AppLockerPolicy) to produce and test policies before rolling out. AppLockerGen’s promise to simplify the XML editing and to provide testing-focused utilities maps directly to that pain-point and could reduce human XML errors — if implemented and used correctly. (learn.microsoft.com)There’s also a broader context: AppLocker is part of a layered application-control strategy. Organizations often combine AppLocker with Windows Defender Application Control (WDAC), Endpoint Detection and Response (EDR), and other device-control measures to achieve robust protection. Tools that make policy generation easier should be considered in a broader defenses-in-depth plan rather than as a single silver-bullet control. The ecosystem of community tooling and docs also contains cautionary accounts of AppLocker rules unexpectedly blocking valid software; that real-world context should inform any adoption plan. (learn.microsoft.com)
Verification: what can be confirmed and what requires caution
What can be verified- The project exists on GitHub, is published under an Apache-2.0 license, and contains the main application code (a Streamlit front-end and Python backend) and a README describing the advertised features. The repo explicitly links to a Streamlit app address for a live demo. (github.com)
- Microsoft’s AppLocker mechanics, rule collections, enforcement modes, default rules, and recommended testing workflows (using reference devices, Test-AppLockerPolicy, and the AppLocker MMC snap-in) are well-documented on Microsoft Learn, and these remain the authoritative operational guidelines for administrators. (learn.microsoft.com)
- The effectiveness and security of any third-party AppLocker helper depends entirely on the code quality, edge-case handling, and the test coverage of the tool. The presence of an “AppLocker Inspector” or “pre-built blocking policies” in the UI is useful, but administrators must review the underlying templates and validation logic before trusting them in production. The project’s GitHub repo and demo are the only authoritative places to confirm those internal checks — do not deploy based just on marketing text. (github.com)
- Any claim that a tool “eliminates AppLocker errors” or “guarantees safe deployments” is inherently unverifiable; AppLocker behavior depends on environment specifics (installed apps, directory structure, user rights, localized paths, and signed vs unsigned binaries). Tools can reduce human error but cannot remove the need for environment-specific testing. Mark such promises as optimistic rather than definitive.
Strengths — where AppLockerGen could add real value
- Lower barrier to entry: Many administrators and security engineers are comfortable with GUIs more than raw XML. A Streamlit UI that structures rule creation reduces simple syntactic mistakes and accelerates policy drafting. (github.com)
- Policy merging and templating: Combining multiple policy fragments into a single, validated XML can remove one manual step where human error often creeps in (copy/paste mistakes). Merging is particularly helpful in organizations where different teams supply policy fragments for different application classes. (github.com)
- Open source / auditable: The Apache-2.0 license and public repository allow organizations to inspect the code, run it locally, and adapt or harden it for their own release pipelines — a major benefit relative to proprietary black-box tools. (github.com)
- Integration with known best-practice testing: If the tool integrates or encourages standard testing flows — e.g., exporting test XML and running Test-AppLockerPolicy or using reference devices — it can shorten the test-to-deploy cycle while preserving safety. Microsoft recommends such staged testing explicitly. (learn.microsoft.com)
Risks and failure modes — why caution is essential
- Policy mistakes can brick endpoints: An improperly constructed policy in enforce mode can block essential OS or third-party components, causing mass outages. Such mistakes are not theoretical; admins have reported default-rule and deployment pitfalls that caused major application failures. Always assume human-created policies can break production unless validated. (learn.microsoft.com)
- Default rules are not a panacea: AppLocker ships with “default rules” intended to prevent common breakages, but blindly enabling defaults without understanding environment-specific nuances can still produce large numbers of blocked events. Administrators must craft policies around the organization’s app inventory. (learn.microsoft.com)
- Bypass techniques exist: AppLocker is effective but not invulnerable. Published bypass techniques exist (delegate execution via whitelisted programs, writing to whitelisted locations, DLL hijacking, and using trusted utilities). Any policy generator that doesn’t educate or help mitigate these attack patterns may give a false sense of security. Security teams should use AppLocker alongside other controls such as WDAC and EDR, not in isolation. (en.wikipedia.org, administrator.de)
- Tool trust and update cadence: Third-party tooling must be audited and maintained. An unmaintained AppLockerGen instance could harbor bugs, validation gaps, or outdated templates. Relying on an external Streamlit demo without local code review or pinned releases is risky. The safe path is to deploy a vetted, internally hosted instance with code reviews and CI checks. (github.com)
- Deployment channel complexity (GPO vs MDM): AppLocker policies can be pushed via Group Policy or MDM (Intune), and differences in how these channels apply policies can cause mismatches. Admins must be aware of XML format and segmentation requirements when deploying via Intune (for example, Intune can require separate XML blobs per rule collection). Community reports and Microsoft Q&A threads show admins hitting deployment errors when combining rule collections incorrectly in MDM. Treat the deployment format and packaging as a first-class validation item. (learn.microsoft.com, reddit.com)
Practical, security-first deployment checklist (recommended)
- Inventory and plan: Build an application inventory per business unit. Document required executables, script hosts, installers, and DLLs. This step is essential before policy drafting.
- Use a reference device: Follow Microsoft’s guidance to create rules on a reference device and automatically generate baseline rules where appropriate. (learn.microsoft.com)
- Draft with AppLockerGen (locally hosted): Clone the AppLockerGen repo, run it locally, and use it to draft policies. Do not rely solely on a public demo instance. Review the exported XML before any deployment. (github.com)
- Test with Test-AppLockerPolicy: Export the effective policy and use PowerShell cmdlets (Get-AppLockerPolicy, Test-AppLockerPolicy) to verify what the policy will block for representative directories and user contexts. This is non-optional. (learn.microsoft.com)
- Stage in audit mode: Apply policies in Audit only to a pilot set of devices and analyze AppLocker logs (Event Viewer) to identify false positives. Adjust rules accordingly. (learn.microsoft.com)
- Harden default paths and exceptions: Use publisher rules where possible (signing-based) rather than broad path rules. Avoid ad-hoc additions to system paths that can be abused. (learn.microsoft.com)
- Apply incremental enforcement: Move specific rule collections to Enforce gradually (e.g., start with Scripts or MSIs) after pilot validation.
- Version-control and change review: Keep all policy XML under source control and require peer review for changes. Automate basic validations (well-formed XML, schema compliance) in CI.
- Monitor and iterate: Combine AppLocker event monitoring with EDR telemetry and SIEM alerts for anomalous allow-list exploitation attempts or suspicious delegation patterns.
- Maintain cross-controls: Evaluate WDAC for stronger kernel-level enforcement where appropriate, and combine with EDR to detect bypass attempts.
How to vet AppLockerGen before trusting it
- Run the code locally: Clone the GitHub repository and audit the code that produces and manipulates XML. Verify that it validates schema, prevents duplicate or conflicting rules, and warns on known dangerous patterns. (github.com)
- Confirm templates and pre-built policies: Review each pre-built template line-by-line. Templates that claim to “block common applications” should be tuned to your environment; don’t deploy them wholesale. (github.com)
- Test exported policies with Microsoft cmdlets: Use Test-AppLockerPolicy and the Test-AppLockerPolicy piping patterns recommended by Microsoft to enumerate blocked files for given users and directories before ever applying to endpoints. (learn.microsoft.com)
- Validate deployment packaging for your channel: If you use Intune rather than GPO, ensure exported XML is packaged correctly per MDM requirements — MDM deployment can require separate handling of Appx, Dll, Exe, and Msi collections. Community posts show this is a frequent source of deployment errors. (reddit.com, learn.microsoft.com)
Integration scenarios and developer ops
- CI/CD for policies: Treat AppLocker policy XML like code. Store policies in Git, enforce PR reviews, and run automated Test-AppLockerPolicy checks in CI to ensure changes don’t introduce broad denies.
- Local hosting + authentication: If you use the Streamlit UI internally, host it behind authenticated access (SSO) to avoid exposing policy creation to the public Internet. Keep pinned releases and a small set of trusted contributors for maintenance. (github.com)
- Record policy provenance: Embed metadata in exported XML (author, date, change-id) so that troubleshooting blocked-app incidents can be traced back to a specific policy change. Use this metadata in your incident runbooks.
Final assessment
AppLockerGen is a welcome addition to the toolset for administrators who must design and manage AppLocker policies: it lowers the friction of editing AppLocker XML, encourages import/export workflows, and — because it’s open source — lets organizations vet and host the tool themselves. The GitHub repository and README confirm the project’s intended features and licensing, but the tool is not a substitute for rigorous testing, environment-specific planning, and layered defenses. (github.com, learn.microsoft.com)AppLocker remains effective when correctly applied, but it has well-documented failure modes, deployment nuances, and bypass techniques that require attention from security practitioners. Use AppLockerGen as a drafting and validation aid — not as an automated deployment shortcut — and always follow Microsoft’s recommended testing flows (reference devices, Test-AppLockerPolicy, audit staging) before flipping enforcement to Enforce. Keep policy XML versioned, review templates and inspector outputs, and pair AppLocker with WDAC/EDR and logging to close practical gaps. (learn.microsoft.com, en.wikipedia.org)
Conclusion
Simple tools that abstract complex XML into friendly interfaces are invaluable to busy IT teams — provided they’re used with discipline. AppLockerGen’s open-source approach gives teams the option to self-host, audit, and extend the tool, which is a major advantage over opaque commercial offerings. Yet the price of convenience should not be haste: AppLocker policies touch critical execution paths and can disrupt business operations if misapplied. Adopt AppLockerGen as a policy-authoring accelerator only after code review, controlled testing, and alignment with a mature policy lifecycle that includes inventory, pilot auditing, phased enforcement, and continuous monitoring.Source: BornCity Open Source AppLocker Policy Generator | Born's Tech and Windows World