Windows 10 uses a new shared approach for delivery of Windows Update patches and users with either bandwidth caps or sharing concerns can set options as noted below

Windows 10 uses your bandwidth to help strangers download updates
https://grahamcluley.com/2015/08/windows-10-bandwidth-updates/

In some ways, Windows Update Delivery Optimization (WUDO) sounds really cool:  Windows Update Delivery Optimization lets you get Windows updates and Windows Store apps from sources in addition to Microsoft. This can help you get updates and apps more quickly if you have a limited or unreliable Internet connection. And if you own more than one PC, it can reduce the amount of Internet bandwidth needed to keep all of your PCs up-to-date.

But here’s the next bit: Delivery Optimization also sends updates and apps from your PC to other PCs on your local network or PCs on the Internet.  Yes, you read that right. WUDO doesn’t just look for computers on your internal network, but – just as if you were downloading a torrent of a Hollywood movie – it will try to find other computers on the internet which are running Windows 10, and try to get parts of the download from them too.

And, of course, it could be your Windows 10 PC that is giving a helping hand to those complete strangers’ PCs by *uploading* the data that they are looking for. Microsoft says that WUDO won’t use metered or capped internet connections to download/upload updates, but that’s only the case if you have *told* Windows 10 that a particular internet connection is metered.

HOW TO CHANGE WUDO Default settings

1. Go to Start, then Settings > Update & security > Windows Update, and then select Advanced options.

2. On the Advanced options page, select Choose how updates are delivered. From there you can use the toggle to turn Delivery Optimization off (you will still be able to get updates and apps from Windows Update and from the Windows Store), or disable WUDO’s default setting of potentially downloading updates from, and offering them to, PCs anywhere else on the internet

Windows Update Delivery Optimization (WUDO) – FAQ
http://windows.microsoft.com/en-us/windows-10/windows-update-delivery-optimization-faq