Note I've already provided this info to @NortonSupport. Just putting here in case anybody else notices this behavior.
Current NAV Mac v 7.4, and also prior version 12.10.1(7) are now considering the DropBox.app's helper file "LoginHelper" as a virus and deleting it (not quarantining it).
Tried downloading a fresh DropBox installer, and same detection occurred with a fresh installer too.