lulu

Install command: 
brew install --cask lulu

Name: LuLu

Open-source firewall to block unknown outgoing connections

https://objective-see.org/products/lulu.html

Cask JSON API: /api/cask/lulu.json

Cask code: lulu.rb on GitHub

Current version: 4.0.1

Requirements: macOS >= 10.15

Analytics:

Installs (30 days)
lulu 1,056
Installs (90 days)
lulu 2,661
Installs (365 days)
lulu 11,463