simplewall is a native Windows desktop application that functions as a personal firewall using the Windows Filtering Platform (WFP). It controls per-application network access via user-defined rules and blocklists, including built-in Microsoft spy/telemetry lists. The application provides a full GUI with tabs for applications, services, UWP packages, rules, network connections, and logs, along with a tray icon, notification popups, and a rule editor. It logs allowed/blocked connections to a CSV file and supports real-time network monitoring via TCP/UDP statistics (including ETW-based UDP accounting). Profiles are stored in XML format with optional compression and AES encryption, and filters can be installed permanently, temporarily, or at boot time. The architecture is a monolithic C/C++ Win32 application with a custom utility library ("routine") as a submodule. Key modules handle WFP filter lifecycle, WFP net event subscription, network connection enumeration, security descriptor management, and UI controls (listview, search bar, notifications). The code demonstrates deep Windows internals knowledge, including WFP version-specific callbacks, ETW session management, cryptographic hashing, and digital signature verification. While the application is actively maintained (latest beta v3.9.1 as of July 2026), it is tightly coupled to Windows APIs and contains workarounds for historical Microsoft bugs, leading to moderate technical drift risk. Strengths include comprehensive WFP integration, robust logging, and a well-organized codebase with reusable patterns for WFP security (ACL management) and ETW-based UDP monitoring. Weaknesses include reliance on a private library submodule, hardcoded service/port lookup tables, and Windows version-specific branches that may need adjustment for future releases. The project is suitable for developers seeking a reference implementation for WFP firewall development or a reliable Windows filtering tool.