It may mean inserting your own router between Comcast and the rest of the internal machines. That's how I handle it.

Comcast router/firewall didn't do what I wanted it to do out of the box, so simply adding a new router between that Comcast internet connection and my home computers gave a lot more control.
Get a decent one and it will work for years.

If you really want to make all internet traffic route through one computer and have that computer protected from the internet (as much as is possible) I suppose it could be a software firewall .. but a separate router/firewall seems like a simpler and likely more robust solution.

/edited for simplicity

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Make your sound your own!
.. I do not work here, but the benefits are still awesome