[Someone1234]

Devil's advocate here:

That could just be the default, and the user could disable it. On Windows 8/8.1 the default is for the "SmartScreen Filter" to block "unrecognised" applications from being run or installed. See their FAQ [0]. It can be disabled however.

If someone is smart enough to be installing applications from third party sources themselves, then they're smart enough to flip a switch in a Preferences panel to enable it.

However this does protect the lowest common denominator who these malware are actually targeting (i.e. computer illiterate individuals who will click ads in search results).

[0] http://windows.microsoft.com/en-us/windows7/smartscreen-filt...

[geoelectric]

If it can be disabled, I'm less bugged by it. It's still a lot of friction for the acceptance of open source apps and other "not really appstore-compatible" projects, though.