“Ask” is indeed the default, but selecting “Automatic update” for both “ENGINE” and “PROGRAM”, and deselecting “Ask for reboot” and “Show notification box after automatic update” would indeed download and install updates automatically and silently, with the install being completed after the next reboot.
Since all my semi-computer-literate relatives only turn their computers on when they want to do something, and turn them off almost immediately thereafter, this worked great for keeping their AV protection up to speed without them even noticing. Or bothering me.
…that is, until they had to start declining to buy a different version of Avast! before every download, and start declining the installation of an additional browser and/or toolbar after the next reboot.
I find it hilarious that the Avast! installer would add a toolbar that the Avast! “Browser Cleanup” utility would then offer to disable as “annoying”. -JW