I know the general advice is to use a software firewall along with the hardware one in the router but I don't necessarily agree with that. A hardware firewall is by far the most effective type you can get. The ones found in modern routers will do all (and more) that even the best software ones can achieve. I rely solely on the one in my router.
Now comes the big BUT.... I also don't go round inviting hackers on board by opening emails from people I've never heard of, opening attachments from those same people, surfing dodgy websites or indulging in illegal downloads.
If you don't do any of those things either AND you haven't got any nosy kids who might do them then I would say a hardware firewall is enough. If you want the comfort of a software firewall as well the word on the streets is that Comodo free is one of the better ones.
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Do you know that we're all in line for succession to the throne? Really?
Well, if forty-eight million, two hundred thousand, seven hundred and one people died I'd be Queen.