I agree that finer classification is needed. However: if you decide to declare to a user that every individual file that might contain a virus does contain a vi

I agree that finer classification is needed. However: if you decide to declare to a user that every individual file that might contain a virus does contain a virus, that's intentionally deceiving them. It's deciding "X% of the time, this statement will not be true, and we are ok with that" instead of building the uncertainty into the statement itself. So I don't see how this can not be considered lying, unless they believed there would be no false positives.