Little Snitch lets you create profiles for different networks, which means you can create a "Trusted" profile for networks you know are safe, such as your office, an "Untrusted" profile for times when you're connecting to networks you're not sure about, and even a "Cellular Hotspot" setting that is stricter about which applications can send and receive data so you don't blow through your entire data plan with a single accidental download.
One of my favorite features is the Little Snitch Network Monitor, which provides a realtime view of the applications accessing the Internet and which you can use to create new network access rules on the fly.
It's important to note that Little Snitch is also a firewall for incoming traffic. So if you're using this app, you don't need to use Apple's firewall at the same time. But keep in mind that Little Snitch isn't as simple a solution as Apple's built-in firewall. That's not bad, it's just important to understand that the onus is on you to know which traffic should be allowed through your firewall and which shouldn't. While Little Snitch is a fantastic app, may also offer more power than you really want or need.
But, hey, it's free to try, so give it a go.
So, Frank, here's your "gatekeeper" with a complete collection of tools for handling everything you hoped for. Thanks for asking! Hope this was the answer you were looking for.
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