About 100,000 new pieces of malware are released every two days, focused on Windows.
Much of it is state sponsored.
And there are some very, very nasty things coming out of E. Europe. Russia. And China as well. Easier to prevent them from getting into your system, than trying to remove them after wards.
Recently ran DRIVE SCRUBBER in effort to remove a lot of bad stuff from a friends PC. Ran it twice and finally cleaned the crap out of it. PC had literally been shut down by it. Was amusing to watch the cursor go in opposite directions as the user intended ...