except for ones I specifically "ask" for.
If you're like me, even though you have been reasonably effective at blocking pop-up ads, you've probably seen a pop-up or two that starts out with some kind of ''WARNING'',
and goes on to suggest that malware is probably slowing down your computer, and then offers a quick ''free'' download that will scan your computer. It has the appropriate display that would indicate that scanning is taking place, and is recording ''hundreds'' of hits, and indicting that each is ''extreme risk''. After an appropriate period of time, the 'scanning' will complete. There will be a ''Remove'' button prominately displayed. BUT, to remove you must first 'register'. To register you must BUY the program. A real bait and switch effort.
Some experts have suggested that the ''scanning and recording'' is nothing more than a modern day version of the old medicine man, or shell game, as no scanning was actually being done.
Don't fall for some slick marketing ploy. Don't let yourself be scared into buying and installing a program that you might not actually need in the first place. A program that probably won't do a job any better than a 'free' program that might be available, if in fact you feel you need such protection. If you have an interest in a software program, 'google' it up and do a little homework.
Here is a fairly long read on this matter, but it covers most of the bases: