Sometimes there are too many computers or devices to disable Windows update manually or individually. To stop Windows update eating up your Internet’s bandwidth, you can block these individual addresses via your Internet router/modem;
Windows update uses these DNS for updates;
update.microsoft.com
windowsupdate.microsoft.com
Block these addresses via your Internet router firewall in the DNS settings. You should contact your ISP for username and password of the router to modify these settings. Or alternately, you can implement group policy if you have a Windows Server.
Courtesy:
https://www.neowin.net/forum/topic/984862-blocking-windows-update-via-router/
