Free i can't really tell you as it tends to change every so often.
I went from Bitdefender to ESET, cheaper and kinder on your computer resources. I found Bitdefender became quite a hog.
Some might find a premium over kill but i disagree as i do financial trades and what not and i rather have something on top of common sense to protect my system.
In my opinion I would not get a free internet security system. There is new malware created day by day. So your internet security system would need to update its software anti-malware files. Keep in mind, that not always, but sometimes these updates cost the company money. Thats not how business models work. You need a business/service, clients, and capital to pay for advertising costs.