Little Snitch is privacy/firewall software for the Mac from Objective Development Software GmbH that monitors network activity and gives you control and visibility for data leaving your computer via network connections. Features include connection alerts with flexible blocking of outgoing traffic, including on-the-fly control, rules-based configuration (with several aids) and configuration profiles (e.g. for different locations or networks); DNS name based traffic filtering; network monitoring displays and snapshots (with details about traffic, history, hostnames, ports, geographic locations, etc., plus packet capture in PCAP format); an inbound firewall; a “research assistant” database to help identify networks and activities; and much more.
Little Snitch 4.4.3 is priced at $45 for OS X 10.11 and up. A demo mode functions for three hours at a time, for 30 days. (Little Snitch legacy versions support Mac OS X 10.2 and up.) The most recent release updated macOS Catalina support.
Please upgrade to this version before you upgrade to macOS Catalina!
On Catalina, system apps have been moved from /Applications to /System/Applications and the paths in rules must be updated. If you upgrade to Catalina while a previous version of Little Snitch is installed, rules for system apps are not updated.