Windows 8 CP has a free AV/Spyware solution in Windows Defender (re-branded MSE). This may be well for some users, as it auto updates & scans the system for you. Just a few settings to make, notably the time of scan & a few other options.
However, if you're considering this as your permanent protection, I highly suggest adding Malwarebytes Pro Lifetime version. If you were to download it today, it probably upon first opening the program offers a 14 day trial of Pro.
Normally, on the MBAM site, this sells for $24.95. But you can sign up for promos at Newegg.com, and receive daily specials. Usually, once a week or so, it's available for $14 to $15, possibly less, with the discount given, and free shipping. It's a small price to pay for lifetime protection. And if one decides to buy another computer, it can be uninstalled & re-activated with the same key.
Note that if you have the Free version already installed, all you have to do is click onto the Register/Activate link on the left of the screen & enter your key, and you're done. Just as Windows Defender, one can schedule scans & auto updating.
It's a lot of protection for the price, it auto blocks all known malware sites with no interaction. Well worth considering for the price, even if one paid the full $24.95 for it. Install the free version, activate the free trial (if offered), you'll see for yourself.