I think it isn't good to just trust the ISP, you can never be sure they protect you.

I leave the firewall of the router enabled and I only forward needed ports in the router manually so all not needed ports are hidden from internet point of view.

I also have the firewall that come with the antivirus; the firewall of Windows also cannot really be trusted (it is enabled on all pc so it is so common that it is the first to be breached).

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Skulls! Multi-Network WebCache