Follow the link to the FAQ, http://www.microsoft.com/en-us/windows/windows-10-faq:
Can I turn off the notifications?
Yes. Click “Customize” in the System Tray and turn off the Get Windows 10 app notifications in the menu that comes up.
Can I turn off the notifications?
Yes. Click “Customize” in the System Tray and turn off the Get Windows 10 app notifications in the menu that comes up.
I guess one could uninstall :
https://support.microsoft.com/en-us/kb/3035583
Looks like this thing was sleeping all this time on my computer and then woke up on a given signal. Sounds like a virus to me... !