Portmaster 1.0 Release Marks it as a Solid Open-Source Application Firewall for Privacy-Focused Users
Portmaster by Safing is a free and open-source application firewall that aims to automate the process of protecting the privacy of its users. It allows you to monitor network activity, add custom connection rules for applications, and more. We tested it during the alpha stage, and came to the conclusion that it had good potential to act as a viable alternative to GlassWire. Of course, it may not be a replacement, but it can be one in the near future...