Safing Portmaster is an open-source application firewall that monitors and controls network traffic on Windows and Linux systems. The tool provides visibility into all network connections made by applications on a device, allowing users to identify and block unwanted connections. It features system-wide tracker blocking that extends beyond browser protection to all applications. Portmaster enables users to create custom filtering rules at both global and per-application levels. Users can completely block internet access for specific applications, filter connections based on geographical regions, or block peer-to-peer connections selectively. The application includes a monitoring dashboard that displays real-time network activity, showing which applications are connecting to which domains. This helps users detect potentially malicious connections and take appropriate action. Portmaster operates locally on the device and doesn't require cloud processing of network data. It's designed to enhance privacy by giving users control over their device's network communications. The software is available for Windows, Debian/Ubuntu, and Fedora operating systems.