Free Mac security utilities

The site below has several free security utilities for the OS X Mac platform.

https://objective-see.com/products.html

Lulu

LuLu is the free, shared-source macOS firewall that aims to block unknown outgoing connections, unless explicitly approved by the user.

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

Santa

Santa is a binary whitelisting/blacklisting system for macOS. It consists of a kernel extension that monitors for executions, a userland daemon that makes execution decisions based on the contents of a SQLite database, a GUI agent that notifies the user in case of a block decision and a command-line utility for managing the system and synchronizing the database with a server.

https://github.com/google/santa

EtreCheck

EtreCheck is an utilty for Apple Mac OS X.  The application consolidates information from over 50 different diagnostics tasks and displays it all on one concise report.

https://etrecheck.com/