When anti-virus or anti-spyware programs update their definitions - is only new malware defnition ADDED to the existing list of definitions on our HDD’s or is a WHOLE definition list replaced with a new (a bit bigger) one?
It entirely depends on the application.
avast is good in that it does incremental but I wouldn’t like to download the whole database at a File Size: 20.67 MB.
Where SAS is a pain in the rear as it downloads the whole database, but that is currently a little under 3MB. MBAM is the same but its database is about 1.5MB.
So as you can see it differs from application to application.
Cool, thanx. 
You’re welcome.