I experienced the same warning using ESET Internet Security - Microsoft wanting to 'phone home' with the webcam every time I started the computer after performing an upgrade.
As mentioned by someone here with an earlier post, the solution to stop this was to Open up Task Scheduler, navigate to Microsoft-Windows-Device Info and disable the task called 'Device'.
I looked into this further: Apparently it launches a program called devicecensus.exe
You can test this by manually running %windir%\system32\devicecensus.exe .... if what I'm saying is correct for you - and you still have your firewall enabled you will most likely get a popup within a second saying that a device attempted to access the webcam.
For some reason, Microsoft appears to be doing a census / survey on all our devices and hardware on a daily basis at 1am local time, otherwise it launches when the computer is next turned on.
The good news is that it seems as though it's not a virus or malware, and it's a "legit" application by Microsoft that's attempting to access the webcam.
The bad news is that Microsoft appears to be installing an ever increasing number of services or functionality into Windows that consistently monitors us and transmits data back to their servers.