This is one very good reason that computer users (of all brands) should use an AV/IS suite that has a cloud security component within it. Although on Windows 7/XP I use ESET Smart Security 5, I'm using Avast IS 7 (the newest version) with Windows 8 CP. Virus/Malware/Spyware writers are getting more & more intelligent by the day. Cloud based security solutions (or partial ones) provide instant protection to all users through it's streaming protection whenever a threat is found.
Note that when installing Avast IS onto Windows 8 CP, the user may get an warning error (I did) when trying to install the package. The workaround is to install the Free version (AV only), let it offer the 20 day trial of Avast IS, accept it, then enter the key. The first time that I installed Avast on Windows 8 CP, I did this on purpose, just to get the trial, to make sure that it works with 8 CP.
It was on the second install, on my notebook, after purchase of a 3 user license, that I saw that the IS would not install (Windows reported it as incompatible). So I done what I did the 1st time (proceeded to install the Free version), there was a place to enter the license key for upgrade to maximum protection, it worked.
Before Windows 7, I had used Avast Free for years, and it caught most everything that went through it. Today, that would not be good enough. That's why I have concerns about users depending upon Windows Defender as their sole protection on the net. It's just not enough to protect against these type of threats. I have nothing personally against Defender or MSE (except for 1 nasty attack that only a format & re-install would cure), except that if one of these attacks happens, the user is defenseless with these options.
The free options (of any brand) will probably never be good enough, unless the user runs their browser in a sandbox.
Cat