As Guilbert53 indicates, you should have BOTH an anti-virus program AND an anti-malware one on your computer. Further, again as G53 says, unless you've got a 'paid for' anti-malware program (which 'runs in the background'), you need to remember to run the anti-malware program occasionally (as the freebies only 'run on demand'). I suggest running it once per fortnight (or, of course, whenever you suspect that malware might have found its way onto your computer).
I've stopped recommending that people download the free version of Malwarebytes Anti-Malware though, as it now forces you to take a free trial of the 'paid for' version, which has considerably slowed down two of my machines.
While it is possible to disable that trial, it seems simpler to me to start with a program that doesn't create such a problem in the first place, so I now recommend downloading and installing AdwCleaner instead. It's actually produced by Malwarebytes anyway and so uses the same malware databases. (i.e. it should be every bit as good as Malwarebytes Anti-Malware is):
https://www.malwarebytes.com/adwcleaner/