Little Snitch - Little Snitch is a firewall application that monitors and controls outbound internet traffic.
Micro Snitch - Micro Snitch is an ultra-light menu bar application that operates inconspicuously. It helps figuring out if someone’s spying on you.
Gufw - Gufw is an easy, intuitive way to manage your Linux firewall.
Oversight - Get notified when an app accesses your Mac's camera or mic
netfilter - Netfilter software comprises iptables, ipset, conntrack-tools, libnetfilter and more.
TinyWall - Lightweight and non-intrusive firewall