Little Snitch $45 (approx £35)

obdev.at

MacOS’s app firewall is purposely designed to be very easy to understand: it simply allows or blocks apps from talking over the network. Little Snitch offers greater control over which servers, ports and protocols each process can use. The frequency at which it pops up at first can be daunting, but the built-in Research Assistant takes away the worry by helping to identify the purpose of all those system processes it warns about but you’ve never heard of.