I just decided to do a full system scan on a whim.  I did this two days ago.  There were 38 threats detected.  If I just did a scan two days ago and have been running Bitdefender why are there threats on my computer?  Shouldn't they have been caught as they were incoming?  Further, why do I have to run a scan to find them?  Isn’t Bitdefender always scanning my computer and removing them as I go?