Don't understand Watchguard that well, but I'll try my best.
So my computers are continually trying to get Microsoft update. It's disabled in GP, it's blocked in Watchguard, the packets are getting denied, but Microsoft is still the top-reached destination.
Blocking VLAN traffic to these addresses: windowsupdate.comwindowsupdate.microsoft.comupdate.microsoft.comdownload.windowsupdates.comdownload.microsoft.com*.windowsupdate.com
Any other ideas?