LuLu
The free open-source firewall that blocks unknown outgoing connections
Open source
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About LuLu
LuLu does one thing well: it blocks unknown outgoing connections until you approve them. Patrick Wardle's firewall has become the default recommendation for anyone who balks at paying for Little Snitch.
It's fully open source, maintained by the Objective-See Foundation, and the alert flow is simple enough that non-technical users cope just fine.
You don't get Little Snitch's traffic visualisations or profiles, but for zero dollars the core protection is the same idea, and the code sits on GitHub for anyone to audit.
