Backup.exe is distributed by emergency update to all avast versions which are running or newly installed on Windows 7, 8 and 8.1. You may also notice it on Windows 10 only if you upgraded from previous windows version.
pm
A long time Avast user here ...
Besides the fact that we must trust our OS, we also need to have complete trust in our antivirus program. I am still troubled by the fact that the Avast emergency updater can silently install a new .exe file on our PC, that then is able to send stats to a server, harmless or not.
With no popup asking if we would like to install said .exe? Where was the user considered? Trust us, you say? Hmmmm....
I have deleted Avast from my primary PC and chose another vendor. I will still continue to use Avast on my media center PC, which doesn't store any personal or business docs ... I do like the silent mode.