LuLu is a free open-source firewall for Mac developed by Objective-See, the security research organization that produces trusted macOS security tools. The application monitors outbound network connections and alerts you whenever a process attempts to contact an external server for the first time, letting you decide whether that connection should be allowed or blocked permanently.
The connection alert system intercepts new outbound connection attempts before they complete and presents a notification showing which process is trying to connect, the destination address, and relevant process information. Allow or block the connection from the alert. Remember decision options save your choice as a permanent rule so the same process isn't repeatedly prompted — allowed processes connect freely afterward while blocked ones are silently stopped.
Rule management displays all active allow and block decisions in a list you can review and modify. Delete rules to re-prompt for future connection attempts. Edit existing rules to change allow decisions to block or vice versa. Process information displayed in alerts includes the code signature status, helping identify whether the connecting process is a known legitimate application or something unsigned and potentially suspicious.
The block list visibility shows which processes have been blocked and how many connection attempts were stopped. This record surfaces background activity from applications and system processes that attempt to contact external servers in ways users may not expect. Passive monitoring mode logs connections without blocking, providing a record of all outbound network activity for review without actively interrupting any connections during the learning period.
- Outbound connection alerts intercept new network attempts before they complete for allow or block decision
- Permanent rule creation saves allow and block decisions so processes are not repeatedly prompted
- Process code signature display shows whether connecting apps are signed by known developers
- Rule management interface lists all active decisions with options to edit or delete each entry
- Block attempt logging records how many connections were stopped per blocked process over time
- Passive monitoring mode logs all outbound connections without blocking during initial learning period
- Open-source codebase allows full security audit of the application behavior by anyone
- Apple Silicon support runs natively on M-series Macs with full network monitoring capability
- Zero cost operation with no subscription payment or premium tier required for any feature
LuLu represents focused development creating software that excels at specific tasks. The application addresses real user needs with practical solutions refined through actual usage feedback. This targeted approach produces tools that feel purposeful rather than bloated with rarely-used features.
Updates maintain compatibility with macOS releases while introducing improvements based on user requests. The development cycle balances stability with progress, ensuring the application remains both reliable and current.